Clear coat on a guitar is the same deal. Rushed a refinish on an old Strat once because I was impatient. The stuff stayed tacky for weeks and ended up cloudy in spots. Learned that lesson the hard way, just like your car paint. Some things you just can't hurry.
Remember seeing a guy try to rush a nitro finish on a telecaster with a space heater. The lacquer checked and cracked everywhere, looked like a dried-up riverbed. Makes you wonder, is it just impatience or do we not trust the product's own drying time? What's the worst rush job you've seen someone else do?
Yeah I learned that the hard way too, tried to speed up drying on a table once and it never fully set. Why do we always think we can beat the drying time?