Also, searching for previous questions about the same subject is useful. I just did a quick search of the words hand sander and found this Here is a link that might be useful: Hand sander question

Thanks for your comments and I'm sorry for the confusion in my original posting. I should have made clear that the 2nd picture above shows our staircase in the process of being remodeled. It is not the finished remodel. I'll upload some demo and "before" pictures below. I hope they'll help with some of the questions. Here is more background on this project. If anyone reads through this or looks at the photos below and still has structural concerns I would love to hear it along with any reasons for that. This is the last piece of a total townhouse remodel. The staircase has been difficult because of conflicting advice from subcontractors. As you can see in the photos below, the half walls were torn out and replaced with framing for the installation of spindles and handrails. The architect's plan is to replace the carpeting on the original steps and put false treads and risers on the new framing. Those are the black things you see in the pictures (the risers will actually be white but these are just mockups). Our carpenter did have structural concerns with the architect's plan and he backed out of finishing the project for that reason. We brought in a structural engineer. The SE said the new framing was solidly attached to the original treads. He didn't think we needed to put full-width treads under the carpeting for structural reasons. At the time I wasn't thinking about how the steps would look style wise. I was preoccupied with getting the spindles, newels and handrails I wanted. My husband wanted carpeting and I conceded. In hindsight I guess the new carpeting was put down prematurely. We're now finishing the project with a woodworker. Since we have the ok of a structural engineer and the architect confirmed the plan is to code I was hoping the issues about trim and the drywall were the last things to resolve. Thanks for your advice so far on these issues. Unfortunately we cannot start the staircase all over for style purposes only. We would start over for structural reasons if needed. Thanks in advance for wading through all this background.

If there is paint on the oak and the oak is not being painted, that's sloppy. Yes, it looks like he used tape and the paint got underneath the tape. Usually when this happens it is because the person doing the taping used his thumb to press the tape down and since the human thumb is round, it cannot reach the back edge of the tape which is the only area that really needs to be pressed down well since that is where the paint is being pushed into the taped surface. I usually use a thin bladed flexible putty knife to seal the tape at the back edge. Sometimes some paint still sneaks behind the tape, but it should be minimal. Any paint that does sneak behind should be removed after pulling the tape before asking the customer to be paid. At least that's how I would do it.

Thanks for all the feedback. @Patricia Colwell - a couple of them are rough. I'm not sure what type of wood it is. If I don't cover them, I'll have to replace them. I don't want to go back to carpet. That back room and those stairs is the last carpet in the house. I was tempted to consider just carpeting the treads (like the second post I made). I was lucky with the main house stairs, it had oak treads and I just had to clean them up. I guess if I want oak hardwood stairs, there is no magic. Hard work or big payout. As for existing treads, I still can't tell if they are under or butted up against the skirt boards. It doesn't make sense to do it that way, It has to just be well fitted treads. It would take a magician to cut those skirts with every level fitting so well. One more question regarding those three odd shaped treads from the first picture. What is the typical solution? Buy extra treads and use an extra one or two cut fastened together? Or do you order a custom boards from your lumber company? Answer to my own question, for those who are just learning like me. I need to buy/build a left hand winder tread set. Rona and many other places carry them. Done! I have no more questions/concerns with this subject. Thanks for the help. Thanks, Mark.