You might find an answer here but it is very important that you do a backup,
Before you start any of this. .
I followed instructions from the links you gave. iTunes now appears to be running the mp3 files from new iTunes Media folder on my Data partition. So thanks thats was very helpful.
After the reclocating the 35GBs iTunes Media folder and removing the orignal I am still left with very large amount of Audio data (77.4GB) on the drive according to Storage in About This Mac. So I looked under Music the Finder sidebar and I have have folder their simply named "iTunes" which is 88.3GB in size. It seems to just contain music files and music files in folders.
Any ideas how I should go about moving the remaining folder and / or its contents?