What is Rit Dyemore actually good for?

I decided to get into dyeing a couple months ago so I stocked up on all the colors of Dyemore. Now that I've started experimenting I'm finding a bunch of information actually steering me away from the Rit Dyes. For the record I'm trying to do glue-bed dyes. Do I need a new substrate like lotion or shaving cream to make the Dyemore work, or should I just invest in a new dye like iDye Poly?