jennifer,,,first off, the wood is oak, not pine. second, why are you having your painter do anything w/wood refinishing? He should have told you that It won't take the stain because the wood has a clear coat on top that resists anything from absorbing. the top coat could easily be removed with sanding, being careful not to bite into the actual stain. you just need to remove the clear top coat in order to apply a darker gel coat. and if the current products(what is currently on your bannister) used happen to have been water based, an oil based stain will repel against that.
As for stripping, there is a natural green product that i've used that words great. SoyGel stripper.
it's gentle enough that you can use your bare hands and it cleans up with plain water. (the others need a chemical 'wash' after scraping)
stripping those spindles would be an absolute nightmare to do. either get new ones, or paint them. doing the bannister isn't that bad. what you could try is sanding off the clear coat w/a 120 grit sanding pad to try and remove the top coat. you'll see it on the sandpaper as a fine, whitish dust. wipe well w/mineral spirits after sanding to see if you got it all. then go over it w/a darker gel stain.
this one was done with a darker stain like Java.
painting black for the banister and treads, white for the risers and spindles.
if you'd rather update, go w/more of the squared off spindles
this first one is how the walnut gel stain would look w/the white square spindles.
all painted a matte black
Q
stairway. listing photo.
Q