Shawn,

Did you take the door down and lay it flat on a couple of saw horses? Did
you remove all of the hardware from the frame and mask it before you began
polying it? I've used poly on my doors with a cheap nylon bristle brush
without any problems. Was able to put on 3 coats in a day. A good work space
with adequate lighting will help a lot. I found that with light coats the
door would be dry enough after 20 mins to stand up so you can do the next
door. After an hour the poly was dry enough so you could do the other side.
Watch out for drips along the door edges.

Dave M.