Lots of questions on this one hope i answer all at one post.
winding checks are used above foam & cork fore grips. it tapers down the area to the thread and creats a good finished product. some guys don't use them and must have a steady hand applying the finish. they are not needed with cork tape.
size of wrap is up to you longer wraps will add weight and stiffen the blank. I usually go aprox 3/8-1/2 beyond the guide foot
1 or 2 layers is all up to how thick you like your grips. just make sure that they are in the same direction . This way when you file the area closest to blank to taper it they won't unravle then tape with electrial tape.
finishing the reel seat area. These links will show how I do them.
http://www.striped-bass.com/Articles/figure5.shtml
http://www.striped-bass.com/Articles/figure16.shtml
http://www.striped-bass.com/Articles/figure17.shtml
http://www.striped-bass.com/Articles/figure18.shtml
hope this helps