You can try heating it with a heat gun and see if you can kick the epoxy to set. But more than likely it's not going to set. This is the problem with thinning epoxy with alcohol. If you use too much you change the chemical reaction, and instead of setting hard it will stay rubbery like that. If it doesn't set with heat then your best bet is going to be to scrape it off and redo it.

What I prefer to do if at all possible it use a heat gun to spread epoxy. Instead of thinning it out with alcohol, I use the heat to thin it. Use 30 minute epoxy because the heat shortens the set time, and anything less than 30 minute epoxy won't give you enough time to work. But put a "blob" of epoxy in the area you are working on, heat it with your heat gun, and use a epoxy brush to spread it over the area to be worked.

Hope this helps

Ken