Acetone will remove the stickiness, as it will remove any uncured resin. After you use the acetone, put another thin layer of resin over it with a very high amount of catalyst. You must be quick, but the extra catalyst and heat created should kick off the remaining resin. This assumes that there are some parts of the original resin that have cured. From you description it sounds as if this is the case. I have had this problem in the past when working on my boat, and I used the method that I explained above to take care of it.
Good luck.
Kurt