Thanks for the replies, guys.

I've been coloring the piece and my hair using Clairol semi-permanent Natural Instincts hair dye I just grab off the shelf at the pharmacy. Is Wella better? And so it seems using permanent dye is ok? For a while I thought permanent would be harmful to the piece but using semi-permanent has been a pain as it doesn't take long for it to start fading away in my natural hair.

You say you leave the dye on for a minute and a half on the piece - I imagine that means once you've finished dying the whole piece, then you wait a minute thirty, right? How long do you think it takes you to apply the dye? I don't leave my dye on for very long on the piece either, but sometimes I worry I take too long to dye it and parts will become too dark.

I'm thinking of actually getting a blond unit so that it lessens the problems with visible knots. Do you think that will make it harder to match the unit and my natural hair after I dye both? Like would it be easier to match if I just got a brown unit that is somewhat close to my natural color?

Thanks!