Using multiple external drives

So i have an external 4tb G-drive named X_1 that I have iTunes db on and Rb uses as my primary (works fine). I have a secondary drive i just got it's a transcend 2tb external named X_2 it has my iTunes library replicated on it. I would like to use my X_2 to be mobile cause i travel frequently. The X_1 primary works just fine, I have followed the instructions on "Moving Your Rekordbox Database to External directly" to get the X_2 to act as a primary and be mobile with it, however it doesn't work. Could you please explain in detail how can I add my X_2 to act seamlessly as a primary db with iTunes on it?

Also what good dependable flash drives could you recommend, i currently have been using PNY 256GB and lately iam getting an e-8307 error on xdj-rx and nexus cdj-2000? Any ideas and resolutions.

i have a macbook pro running mac os x 10.10.5 / rb 4.0.1
regards
-jsmall