Sure, SMT990 - I'll even go one step further than the steps found on the web, and provide some advice to help optimize in building a bootable USB drive...
1) although you can install OS X on a traditional external hard drive, ideally get yourself a Flash USB 3.0 thumb drive... and the faster the better. The current speed champ is the SanDisk Extreme (I would highly recommend the 32GB model to give yourself the extra space, which I'll explain why in the next step). Btw, the SanDisk Extreme is a very inexpensive drive -- awesome value on Amazon and other online retailers.
2) If you ever want to use your USB drive for not just as an emergency drive but also for moving files between computers, I normally partition the USB drive into 2 partitions (or more if you want), using Disk Utility found in your Utilities folder. Make the first partition your bootable emergency drive, formatted as Mac OS Extended Journaled with 6GB and name it something like "Emergency Disk". Select the "Option" button below and click the option for a GUID Partition Table. I usually format the other partition as MS-DOS FAT for sharing files between Macs and PCs. Or if you never intend to use this USB drive to share files with a PC, then you can make the other partition(s) as Mac OS Extended Journaled.
3) Restart your Mac, and hold down the Command and R keys while powering up to boot into the Recovery partition of your MacBook Air. Select the option to reinstall OS X. When prompted, select the "Emergency Disk" you created on your USB drive, and let your Mac download the full 10.8.5 image from Apple servers -- depending on your Internet speed and server load, will likely take 20 to 40 minutes to pull down the 4.5GB of files.
4) Here's the important trick I recommend, to save the installer file: upon your Mac completing the download, it will automatically restart. As soon as your Mac reboots, quickly remove the USB drive from your MBA and let your Mac take an extra minute to search and then restart normally from your internal drive.
5) Now insert your USB drive back into your Mac, and look for the file named InstallESD.dmg -- that is the full virgin 10.8.5 disk image you want. Ignore the rest. Copy that onto your desktop and keep it handy for future use (e.g. I put it into a folder called "Installer 10.8.5").
6) Now double-click the InstallESD.dmg you just copied to your desktop, and proceed to install 10.8.5 on the USB partition named "Emergency Drive".
Done. Obviously, I would also roll back to the .22 driver on this spare drive.
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Now that you have a clean 10.8.5 on a spare drive for emergency or even testing purposes, I normally tweak it by removing all things off the Dock except tools like Disk Utility and other essentials, and then I usually install good ole DiskWarrior, which in my opinion is still the best OS X commerical repair tool out there.
Hope this helps.