Q: How do I delete 'other' storage without hidden files?

First understand what OTHER consists of:

https://support.apple.com/en-us/HT202867

You do not want to delete all of it.

Download from the Internet OmniDuskSweeper and Grand Perspective (both free) and open them. They will show all of your files and the respective sizes. This should allow you to determine what file to delete or off load to an external HDD.

Do not forget to empty trash. Only then is space allocated for new data.

Ciao.

There is a good chance that they are hidden because they are required for the computer to run properly.

Sometimes reindexing Spotlight can help free up space. You want to drag your entire Volume (Macintosh HD) during step 4, then remove it again in step 6.

Also, if you have any other partitions on the hard drive, any data linked to that partition appears as other. I have 100GB dedicated to Windows 7 and it shows up as Other when I'm logged into OSX

Spotlight: How to re-index folders or volumes - Apple Support

The point is that OTHER (the category) is NOT your problem.  It probably should be called 'Miscellaneous' or something like that. 

One of the 'hidden' or 'unidentified ' files is the OSX which is a part of OTHER.  Usually the hidden files are those that the user should never touch because they often are part of the operating system.  Ignore that name and see what, if any, data should be excised from your MBP. 

Ciao.

For information about the Other category in the Storage display, see this support article. If the display seems to be inaccurate, try rebuilding the Spotlight index.

Empty the Trash if you haven't already done so. If you use iPhoto, empty its internal Trash first:

          iPhoto ▹ Empty Trash

In Photos:

          File ▹ Show Recently Deleted ▹ Delete All

Do the same in other applications, such as Aperture, that have an internal Trash feature. Then restart the computer. That will temporarily free up some space.

According to Apple documentation, you need at least 9 GB of available space on the startup volume (as shown in the Finder Info window) for normal operation—not the mythical 10%, 15%, or any other percentage. You also need enough space left over to allow for growth of the data. There is little or no performance advantage to having more available space than the minimum Apple recommends. Available storage space that you'll never use is wasted space.

When Time Machine backs up a portable Mac, some of the free space will be used to make local snapshots, which are backup copies of recently deleted files. The space occupied by local snapshots is reported as available by the Finder, and should be considered as such. In the Storage display of System Information, local snapshots are shown as Backups. The snapshots are automatically deleted when they expire or when free space falls below a certain level. You ordinarily don't need to, and should not, delete local snapshots yourself. If you followed bad advice to disable local snapshots by running a shell command, you may have ended up with a lot of data in the Other category. Ask for instructions in that case.

See this support article for some simple ways to free up storage space. A common waste of space is old iTunes backups of mobile devices. As illustrated in this support article, select the Devices tab in the iTunes preferences window, select the backups you want to delete, and click Delete Backups. Keep at least one backup of each device that you still use.

You can more effectively use a tool such as OmniDiskSweeper (ODS) or GrandPerspective (GP) to explore the volume and find out what's taking up the space. You can also delete files with it, but don't do that unless you're sure that you know what you're deleting and that all data is safely backed up. That means you have multiple backups, not just one. Note that ODS only works with OS X 10.8 or later. If you're running an older OS version, use GP.

Deleting files inside a photo or iTunes library will corrupt the library. Changes to such a library must be made from within the application that created it. The same goes for Mail files.

Proceed further only if the problem isn't solved by the above steps.

ODS or GP can't see the whole filesystem when you run it just by double-clicking; it only sees files that you have permission to read. To see everything, you have to run it as root.

Back up all data now.

Install the app in the Applications folder as usual. Quit it if it's running.

Triple-click anywhere in the corresponding line of text below on this page to select it, then copy the selected text to the Clipboard by pressing the key combination command-C.

For ODS:

security execute-with-privileges /A*/OmniDiskSweeper.app/*/M*/* 2>&-

For GP:

security execute-with-privileges /A*/GrandPerspective.app/*/M*/* 2>&-

Launch the built-in Terminal application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

Paste into the Terminal window by pressing command-V. You'll be prompted for your login password.

The application window will open behind other open windows. When you scan a volume, the window will eventually show all files in all folders, sorted by size. It may take a few minutes for the app to finish scanning.

I don't recommend that you make a habit of doing this. Don't delete anything as root. If something needs to be deleted, make sure you know what it is and how it got there, and then delete it by other, safer, means. When in doubt, leave it alone or ask for guidance.

When you're done with the app, quit it and also quit Terminal.