Ive been doing fiberglass for years. I buid molds and manufacture parts out of them. All using epoxy. I agree with the acetone solution. Ive been using that for years to thin epoxy resin.

From what you are saying, you have tried all that is mentioned and you still are getting a sticky result. I would suspect a bad batch of epoxy. I have had it happen to me before.

A few more things that will mess with you when doing finishing resin. If the humidity is high, like 80% or more, moisture from the air will be attracted to the resin and you end up with what I call a "rubermaid" finish. It will have a whitish hue to it and feel like rubber instead of hard epoxy. It will also have a "sticky" feeling to it.

Check those two things out. Bad epoxy or high humidity during the process.

If you suspect humidity, you can use a large box ( big enough to put your part in your glassing ) and using a heat sorce ( light bulb works good ) put the part in after applying the resin and heat it to about 120 to 140 degrees for an hour or two. It wont take long to set the epoxy off at those temps. The heat will also help with moisture control. Short of a climate controled heat booth, thats bout all I can suggest.

Good luck and hope this helps.

Warbirdguy