I have ordered some Worm Dye to attempt my first dye job. Any suggestions on how best to control it (spreading, masking, etc.)?

Check out the 'First time die' forum (page 5?) and 'Dying Discs' for lots of info.
I'm still experimenting with application techniques for worm-dye. It's very thin and it dyes immediately, so any mistakes made are permanent. It's also acetone based and a bit toxic and highly flammable so be careful.
I've used syringes, eye-droppers, straws, camel-hair brushes,
sponges, sponge brushes and rags with varying degrees of success.

Have you ever gotten it to turn out very dark in comparison to Rit Dye? I was wondering if anyone adds anything to it to get it to set more uniformly. Like you said its pretty light.