Arctic Silver's website states that you can skip the tinting with AS5. I did it the first time I used it, because I had used AS3 before, but the second time I used it I skipped the tinting. I didn't notice that much of a temp difference between the two methods though.
Basically, with AS5, you want to use as little as possible to do the job. Less is more in this case. I like to "butter" the core with a super-thin layer of it using a razor blade, and that seems to work best for me. Others just put a small amount in the middle of the core (about half a grain of rice) and let the pressure of the heatsink mount spread it.
Take it off, clean it up good with some 91% isopropyl alcohol, and try a different method. Remember too, that AS5 takes a week or two to settle in, and you'll see significant temp drops as this happens.
Good luck!