In order to figure out if you need to clay before waxing, feel the paint. Wash the car then touch it. If it's bumpy, gritty and doesn't feel like smooth glass it needs to be clayed. You can also put your hand in a sandwich baggie and feel the paint it amplifies your sense of touch.
Claying shouldn't take hours...I personally love the surface speedy prep towels, takes 15-20 minutes to clay a car. Just remember to break the towel in on glass before using. It's advertised to last I believe 50+ times.
2001 Topaz Blue 325Ci 64-120k miles SOLD
2003.5 Silver Gray M3 70k miles