My dad and uncle ran a small upholstered furniture company in the 60's and used hide glue for frames. When the company was sold I acquired a 50 lb bag and 2 qt Hold-heat glue pot. It took me about 20 years to use up the bag but glue pot is still going strong.
I don't heat glue in an open pot like Patrick was doing. I put water in the pot and glue in a plastic bottle in the water. That way I have hot glue and hot water for glue up. When I'm finished I put glue in refrigerator or freezer.
Hide glue is technically reversible and veneer is easy, joints not so easy. If it's really cured/dry joint then moisture has to be reintroduced. For joints with high glue line to joint surface like a dove tail or a panel its not to difficult. But for a M&T that's a different task. For a uncured joint then heat from an iron or heat gun will loosen the joint.
Hide glue is transparent in small amounts(thin layers not blobs). Don't expect a large blob to just disappear. It's been my experience that glue is less visible under natural finishes such a Linseed oil and Shellac but lacquer and Waterlox, not so much. If I see glue, I remove qlue.
If you ever do bent laminations you should try hide glues. I had rather work with hide that catalyzed or epoxys.
You can make it water proof by applying formalin to the joint before or after glue up. But be careful formalin fumes don't mix with granulated glue.
I could go on and on ....
I have been getting glue from Bjorn Industries for years. When I first starting getting it from Eugene you just called him and ordered it. He would ship it with and invoice and you would just send a check after you received it. He now has a web site.
selling the best quality hide glue for over 25 years!
Most of the glue(I'm sure Behlem/Mohawk is because I asked them) sold in small quantities is 251 which gells fairly quickly. Woodcraft sells some.
Eugene Bjorn is a wealth of info about glue and likes to talk about it, just give him a call.