i had those problems also. best thing that works for me is just cleaning the shafts with water. sometimes i use a little dishwashing soap and rinse with warm water. when i put the clamp down i slide it back and forth a couple time (it'll probably only slide 1/16") to make sure the glue gets all over the base of the vane. i then hold it down for about 10-15 seconds. i'm using some kind of instant adhesive. since i switched to cleaning the shafts with water only i've had no problems at all.
Ahhhhh, finally someone has seen the light.
Clean the shafts with regular ole water, let dry and glue away. I have used AAE fast set gel, Goat Tuff, Quantum, Zap-A-Gap, and regular ole Crazy Glue gel all with equally great results.
I fletch all my arrows with the rear of the fletch at the step on the clamp. If that is too close to your face you can move it foward as you see fit.