Hello Anton.
Have you checked out these tutes some really useful ones here.
http://www.simmerspaintshop.com/foru...hop-tutorials/
not necessarily what you are after, but good nonetheless.
The bad news is that there really is no easy way of doing these things.
Really the only thing I can tell you is to experiment with different sized brushes and layer opacity/and layer settings like multiply/overlay etc. Also dont be afraid to use the Gaussian blur filter, I use it all the time. And build up your shades and highlights slowly, I never achieve the desired result with a single layer, it can take dozens.
Remember that you are aspiring to the level of(some freakishly good) guys that have been doing this for some time, and you aren't quite at that level just yet, so be patient practice and you'll get there. Ive been in the exact same position that you find yourself in, and I think my work is pretty ok these days.
If you can, search back to when I (or anybody else) first started posting threads here, you'll see that you aren't all that far off getting it right.
Chin up and practice, you'll get there, I'm sure.