It should be very thin but not so thin that it doesn't cover the processor . Sounds like you did everything right, what temps were you running and how long did you run it before shutting it down . Don't worry about cooking your processor the laptop will shut itself down before that happens . There is a break in period for thermal paste. It kinda heats up and melts out a bit before setting into place. Just because your fan ran fast on startup it could be just a momentary condition . Let it run a few minutes and check your cpu temps a safe temp range is from 80 - 175F it will probably grey out at 190 but I have seen a mac at 212 and still running