paint stripper , tack off the knobs and plates it might take more than 1 try. jasco ,biz , dads easy spray theres a bunch of diffrent kinds. make sure you were gloves and have proper ventilation. i would do 1 and see what a task your in for , sending them out to be striped might be more cost effective .
Stripper may react with the brass (chemical components may have reaction)I would try Goof -Off found at most harware stores and m enards,h ome depot,l owels. We have used it on brass,copper,and aluminum without any problems. Alot cheaper too.
these are painted with oil if there a hundred years old. boiling them in water wont do a thing. goof off is mainely maid up of xylene & methyl carbitol and it will work . a convention stripper is mainly methyl ethyl ketone wich will work better its stronger . it mightr mess up brass but i dont think it will . thats why we just do 1 to see.
You could also use lacqeror thinner,this doesnt affect brass either. Get a gallon pail and let soak for 10 minutes and should be able to get it off. Like I have said before not knocking your strippers m.d. just dont like them or use them is all to many bad experiences with them. I will try that behr #500 though and check it out.