My first time on a quad was a little honda that had a centrifugal clutch, so I only had to worry about shifting. After I learned a clutch in a car/truck, when I hopped on my friends’ blasters and banshee’s it was easy for me. Also, a guy at work has a midget race car that has a zuke 1-litre and running gear, with the hand-clutch located on the shifter, so I got some more practice easing out the clutch to get that thing moving.
For learning in a car, I’ve found that using a car that needs to have the clutch replaced makes it a little easier, or one that has a HUGE friction zone. The clutch will usually slip enough that it is forgiving when you dump it out too fast. The problem is that you don’t really learn to ease it out, but it gets you started.