at idle i'd suspect they should be barely warm. But what you should be concerned about is when it is load and the CPU says 75degrees, and the heatsink is still barely warm.
That being said, there's lots of different ways to do the thermal grease, and probably most of them will work. But proof is in the pudding.
If you are getting unhappy results with 1 method, maybe you should try a different one to see if it makes a difference.
Anyway,
The technique I use, is first use alcohol to clean everything up. Everything should be shiny at this point.
If you can, use lint free paper to do this work. Coffeefilter is cheap lintfree paper if you can just grab a couple of those.
On the cooler contact side, i use the buffing technique. So I put a small dab of grease on there, and just use lint free paper to rub it around and rub it off. You shouldn't see any grease but it should leave the cooler surface dulled and fill in any micro-sized grooves.
On the cpu side, I go with the small mini-pea sized blob in the middle. Squish it down evenly, and give a little twist and wiggle each direction way before locking it down. If you want to check your size of your blob; you can do a practice run, and just immediately undo it, to see if your squished blob covers all of the middle of the cpu and gets to all 4 sides (in this technique the corners are fine if they don't get touched).
If you do a practice run, i redo all the previous steps to cleanup first.
Other people go with the use finger in a plastic baggie and just spread a thin even layer on the CPU.