I never injected, so I can't help you there. There are many members on here who do and are very good at it. Hopefully, some will chime in.
Things have changed quite a bit since I poured. There are many more options now.........many that I never got a chance to try. I used MF Super Soft plastic almost exclusively, and added softener, hardener, salt, etc as needed. As for glitter and color, you will find that many companies vary. Most of my colors and glitters came from Lure Craft, with a few MF products tossed in.
I have heard nothing but good about companies like Bass Tackle and Bait Junky's, and I'm sure those are well worth checking out too.
You will learn as you go, hopefully not like me: by mistake. LOL