I've done more than my share of interior walls with wallpaper/paint issues.
There is, in my opinion, no one single way to remove what your walls have accumulated over the years. Often I see oil based paint over laytex over paper over oil base with another layer of paper, then a few more coats of paint.
If this is the case I pull all the trim and start the slow process of wetting/scrapping/wetting until the plaster finally appears.
On really difficuly jobs we may even install new drywall over everything. That's the case on the job we have now. The last homeowner stripped everything down to the studs in this 1895 home. Installed new drywall and then papered over it without a primer coat on the drywall. You cannot remove the paper without tearing into the drywall. Water just makes a mess in this situation.
On several jobs it's been easier/quicker/best results to strip everything back to the studs and start fresh. Keep in mind there is a crew working on it. Also the flooring either comes up first or it's going to be replaced.
There just isn't a quick fix for a problem that has been magnified over many years. It's gonna take a lot more time than you think but you will be rewarded with the results. (Also, you'll give pause before you hang another sheet of wallpaper again...
Just my 2¢