Hand over hand is super hard to do with toddlers. They generally would rather "do it themselves", which makes it hard to guide them sometimes. It's especially so at that age. Ironically it's easier when they get a bit older. Go figure.
It's better just to model writing/drawing yourself and let him watch and try to imitate. If it's something he thinks is interesting, he'll naturally want to do it to. If he doesn't want to, then no big deal.
Almost all kids learn through play and prefer that (because that's what "normal" children do. The ones who don't usually get referred for autism screening, after all). The compulsion to play is as natural as breathing. (It's just as true for young animals as it is for humans, it's our biologically determined way of learning to function in the world). If you watch preschool teachers, early childhood educators, and therapists working with children, most of what they do appears to be "play" but it really isn't. "Play" lowers the barriers to learning, reduces anxiety, and helps children feel more confident as they develop new skills. This is actually true for teens and adults too, it just looks a little different.
So don't worry about it. It's normal. As they say, if you can't beat 'em, join 'em.
Another thing to keep in mind is that young children have short attention spans, and tend to get tired of things quickly. It's better to do things a little bit at a time over a sustained period of time, than to try to do a long session. If he's resisting, then you can be sure he's not learning anything, and it's a waste of time to continue.
Specific ideas to make writing more fun:
1. Sandpaper tracing letters
2. Letter magnets (or words) to rearrange
3. Dry erase boards or chalkboards
4. Huge novelty pencils or jumbo crayons
5. Environmental print scavenger hunt (go outdoors and look for specific letters or numbers on signs).
6. Storyboards: narrate a story and illustrate it together.