Try a real paint store for the Dirtex. If it were me, I would probably skip the cleaning entirely and just sand them really well. But, the reason we always say to clean and sand is because a lot of people don't sand very well, plus some contaminants do not come off with sanding...grease, glue, ground in dirt, etc so that is why we may sometimes need to clean. I do agree though that I would not get wood wet that I am going to paint if I don't have to. I'm just thinking here that wood steps covered with carpet just may not be that dirty. Use 150 grit. Also, if you use TSP, it has to be rinsed pretty well, which is a pain and is why we avoid it for most general cleaning.

The question of, "why do I need to clean if I'm going to sand" hit me last night. The steps are pretty clean.

I was at SW yesterday and the only Dirtex they had was the spray kind. That's all I'm finding anywhere here. I saw some other cleaning stuff like Krud Kutter etc. but didn't look at them too close.

I have a hand sander I'm going to use. Have all my sandpaper etc. you recommended in my last thread about my stairs ready to go. I really like that Ready Patch stuff. Tried it on a different project and it was much easier to work with than stuff I've used in the past.

So as long as I sand well and clean off all the dust (use tack cloth?) I should be ok without the powdered Dirtex? I'm going to pass on the TSP and water idea.

In my opinion, yes. Of course, some people will advise to clean every time no matter what. Honestly, I have never used a tack cloth either...I know I'm a big rule breaker. I just use a dust brush or a towel.

Sounds good to me. Thanks! I'll post some follow up pics once I get it all done.

I agree with paintguy (well, I'd seem foolish to disagree with anyone named that...but anyway!)
Just sand the tarnation out of it and wipe with a dry micro fiber cloth. You'll be all set!