I have sprayed several gallons of T-bird epoxy and fullerplast, as well as Sherwin Williams Conversion varnish. T-bird epoxy is by far the best. If you don't have a spray booth, you can wet sand and buff the finish to remove any dust.
If a finish dries too fast it leaves visible sanding marks under the finish(on glass bows). They are usually more visible on the edge's of the limb. I have not used t-bird polyurethane, but I have seen several bows that did. Both bows showed sanding marks under the finish as well as an uneven,lumpy texture.
Having said that, let me say that all will provide adequate results. I'm just picky. I mean, if I'm going to pay $100 per gallon why not get what works best.