It's not terribly stressful on your players but if they're put in the right sections it will give you the desired improvements.
Most are self explanatory but I'll put a list here to help out :
Goalkeepers - used for GK's
Defender - used for CB's
Full Back - used for RB/LB/RWB/LWB
Def Mid - used for DM but it could also be used for a CM that you want to be more adept at winning the ball.
Midfielder - used for CM/RM/LW (Though if you set the LM/RM to a winger, I'd recommend using the Winger training).
Att Mid - used for AM but it can also be used for a support-based center forward/deep lying forward to improve their passing/support game.
Winger - used for Wingers. Can also be used for RWB/LWB in a 5-3-2 formation where the wingbacks as set to attack constantly while still providing a slight defensive boost.
Striker - used for Strikers but it can also be used for an attacking midfielder you want the player to be more adept at scoring goals instead of assisting.
The same goes for youth.
I haven't had a full chance to see how it assists in attribute building but if FM10 is anything to go by, with the few tweaks I've made to bring it to FM11's training it should work at building attributes pretty well.
How to download:
If you are using FireFox don't left click on the download button... but instead right-click on it and select 'Save link as'. Otherwise, it will try to read the file and come up with error.
If you're still having trouble, try the RS mirror: http://rapidshare.com/files/429568625/HT.tsh