So many times. A woman sat on the stairs (it's usually a woman- men can't be bothered), up to her neck in scrapers and Nitromors burns.
I might be working there for weeks. She's always there. scraping. It's a laborious job. As far as I know, that product is as good as anything else. Works on the "poultice" principle. Paint it on ... wrap up in polythene ... wait for it to work ... then peel off.
Actually, it can be very effective on flat, uncomplicated surfaces. Mouldings are another story..... especially stair spindles. Maybe several applications, and a lot of work with pointy scrapers.
Ric, I'm sure your spindles are most elaborate and shapely. Although the process is similar to leg-waxing, it usually takes much longer.
I would certainly remove the spindles at least, and have them stripped. Actually I think I would take the handrails as well... even though, as in OG's case, some patching is needed afterwards.
Unless the staircase is almost free-standing, probably best to leave it in place. Paintstripper poultices work well on treads, risers, and strings (the side bits that everything fits into).
It's a labour of love, Ric.