Been a while. We did soap tan (buckskin) for deer and mostly bark (tannin) tan for fur bearing animals. I remember us trying chrome tan once but I don't think it worked very well as we had no idea what we were doing with that. How hard it is depends a lot on the type of animal, sheep are almost self tanning, deer aren't to bad, cow or elk or moose are a lot thicker so a lot more work. Most of the fur bearers skins aren't to thick so weren't terrible, mostly coyote and fox by us, never tried a beaver so can't specifically speak to that one.
A few things I learned.. You can't flesh them to well, you have to get ALL of the fat off at least. Any little bit can wreck the tan especially with fur on tannin tanning. Getting the hair to set can be a bit of a trick, a proper pickle does help... managing the PH/amount of tannin in your tanning bath so that it's high enough also helps. Finally working the hide in by hand is IMHO by far the hardest part. You have to work it, and keep working it, and make sure you get the edges all the way until it's plumb dry. You can wrap it and take breaks but it's a lot of working on it. We had a stitching horse like setup with a smooth post sticking up in front of you to work them over for smaller stuff. For larger hides (like deer) we'd stretch them on a frame and then use a smooth ended stick to kind of push on them covering with damp towels and a tarp in between.
If I had to recommend one resource it'd be the old book "Tan Your Hide!: Home Tanning Leathers & Furs by Phyllis Hobson". Is it perfectly accurate? no there are a few bits in there but overall I'd say it's one of the more accessible and useful books on the topic.
