i dont know if it would get ruined sitting at your door. some people love orwg, i dont find it much different from other white glues, except that i find it hard to get off my head and that tiny little brush it comes with is ridiculous.
many people use nx gen unifying agent, ghost bond xl etc, which is why i suggested the sample pack. each glue works different for each person. why go trying full size bottles when you can try a sample of each is my thought.
anything with color can stain the base. i havent used back2natural, i have used aufero which is basically the same thing, you can order it from hair4all, but i suggest contacting them first because they are in the UK. i am currently waiting for my order to arrive and i'm in the states.

i dont have a styro head and i have never stained my base with dye or color conditioner.
i do it off my head. generally i just pour a little bit across the teeth of a comb and carefully comb it through. when using the conditioner i dont think its all that important to get down deep anyhow.