Ok, I found a visual aid for the got2b thing:
Good suggestion in that clip about doing a second coat to smooth out all the holes.
For actually coloring the hair, you get your color, you get your 10 vol developer, you combine them (usually in a 2:3 ratio), and what i like to do is let it develop in a bowl until it darkens a little bit = less time on the hair = less damage to the hair, and easier to see what you're doing.
Instead of dunking your comb, maybe put the color mixture in a narrow tip applicator bottle and squeeze some onto a section of the comb... or better yet, brush all the hair back, and just kind of coat the exposed hair with color using a tint brush if that makes any sense, *then* comb through. I think that will be even easier, and if you get one with a rat tail or pin tail end, you can use the tail end of your tint brush to divide and separate the hair methodically when you go in to do the roots with the little razor cleaning brush. I'll try to find a visual aid for that too.
If you're just doing the front inch, color the roots and ends in one shot imo. Even with no experience. Don't apply any pressure with the razor brush when you color the roots. Feather light strokes are just the ticket. If you do that you should be able to get it super close, with virtually no blonde root showing. A tiny bit of blonde in the root can soften a hairline that's too dense, though.
Yeah you can rinse everything together. Hold the piece upside down under running water until the water runs completely clear, so that the color runs away from the base. Once it runs clear, turn it right side up so that got2b product doesn't run into the hair. It's not actually glue by the way, just strong hair gel. It'll take a while to rine that out, just be patient it will all rinse out with water.
Hopefully that covers everything.