I just finished stripping the paint off my 1910 staircase! I think the wood is fir. I used a heat gun to get the 2 or 3 layers of paint off, and the wood has a dark mahogony looking stain which I really like. The heat gun didn't remove the sticky finish over the stain. I'm stuck as to what to do next. Should I use a chemical stripper to remove the varnish/finish and bits of paint still remaining in some of grain? I'm worried that this will affect the stain. Also is it recommended to stain over top of the old stain? Any suggestions would be greatly appreciated.