Indeed, back in December 2015 this was all new to me too. Just FYI to be on the safe side, a small guide:
1. Cut the parts from the sprue using precision pliers or quality nail clippers like these: http://tinyurl.com/y8m9v9gx
You should be able to cut the sprue precisely clean off, where it's attached to the model part, in order to avoid sanding work.
2. Then rinse the parts in a bowl of water and scrub them down with a soft toothbrush. This step is very important as you want to make sure no nylon powder residu is left in any creases.
3. Have your Rit Dye Liquid and/or Rit Dye More ready (both come in bottles, each bottle 207ML ) for your custom mix in a measuring cup. I would advise two thirds of dye and one third of water for the average dye bath. For the arms on my Kup I used 50% Rit Dye Liquid Teal and 50% RIt Dye More Kentucky Sky.
Then, pretty much follow the instructions from the Rit Dye lady : https://www.youtube.com/watch?v=a23MWZyL-fg
She uses tongs to fish her items out of the dye bath but I would advise a metal sifter, so you won't lose the smaller parts and all parts can be lifted out simultaniously. Timing is of the essence.
4. Once you are happy with the dye, rinse the parts off under running tapwater and let them dry.
goodluck & best regards,