I've used rabbit skin glue, but for custom framing and gilding. It has been used for centuries both for making "compo", which is the sculpting material for frame detailing, and as an adhesive for the metal leaf in gilding.
There are easier, more modern options but for restoration or historically accurate reproduction, it is still used.
Compo is still the best option for getting sculptural details to stay on wood. It's mostly a mix of clays, fine sawdust and the glue. It's hard, stays stuck to the wood and holds up really well. It's fairly water resistant as well, once set. I've seen pieces that are 200+ years old and they are still solid.
I've only used the purchased fine pellets, never handled homemade. For keeping it warm, we used a crockpot on low, with water in it as a warmer. Just had a spacer on the bottom so the pot didn't get direct heat from the crock. They are pretty cheap and easy to find in the thrift stores so I recommend just having a craft specific one. The smell wasn't terrible, but I wouldn't want it on food.