Since a riser gets very little foot traffic, I wouldn't suggest oil base primer as needed. Prime it with a waterborne primer and two full coats of acrylic enamel like Super Paint.

Bumps, nicks and smudges can be easily touched up by repainting the entire riser as needed. A riser takes 5 minutes to paint.

I will have to disagree, wall paint and feet don't match. Better to use door paint, able to withstand a lot more punishment, and it is oil based. And feet with shoes do scuff risers with standard paint pretty easily, no guarantee your stairs wont see its share of shoes even though your say no shoes household.

SP is more than wall paint. But to each his own. If you want something to guard against those shoes that are prohibited, use Pro Classic. Of course that has a learning curve, so practice first.

Oil based paint is not that much more durable than a good acrylic paint these days. No matter which paint you use, stair risers take a beating and they are going to need touch up maintenance or cleaning every so often. This is one of the reasons people often put a carpet runner up the middle of their stairs.