t-shirt forums is a good place for this; you do have to wade through some advice from the less experienced, but there is a lot of content there on this. When you say "digital printer" it would be either an ink jet or Color Laser to produce the images. I buy a fair amount of CAD PRINTZ from Transfer Express, and their CAD-PRINTZ clear. Sublimation can be either inkjet printed onto transfer paper, (I make coffee mugs this way) or it can be printed directly onto cloth, then heat set with roller heat presses. One of my neighbors does this, very impressive to see it in action. Anyway Dan, TSF is a good place for this info...
Steve