Can I refinish hardwood stairs covered in glue?

I had a customer in Denver who was very interested in having her old fir treads, a read oak landing and a red oak step refinished. The only problem was that they looked like this…

So first things first, I had them tested for asbestos.

All clear, no asbestos. Now with my Clarke Super 7R edger and some Norton 40 grit red heat paper, I can get to work.

All of the nosings and corners are still hand scraped and hand sanded. After that I cleaned the treads, sealed them with Bona Classic Seal and put a coat of top of the line finish on them. Bona Traffic HD. The next morning they looked like this:

Now I sanded them smooth with a 150 grit Norton screen. Filled some cracks and holes with some Varathane non hardening wood putty. Cleaned the stairs again by vacuuming and tacking them. And finally got to put on that final coat of extra Matte Bona Traffic HD. This picture was taken after that and while the stairs were still wet.