Dirtex would even be fine or just plain water and a scrub brush. All you want to do is remove the surface dirt that has collected there so that the paint will stick to the siding without the dirt being in the way. You only want to use TSP is you plan on rinsing the areas you cleaned very well.

Just wanted to show this in case anyone was thinking of using Rubio Monocoat. I think it is a beautiful finish! I did a test board on our white oak flooring of the super white color. We sprayed some water first to pop the grain so it would accept more white. The photo has more pink in it than in real life, for some reason. The closeup shows the color better. In the first pic you can see it against my currently polyurethaned white oak unstained floor. On the left is the maple stained sample of my island. I have spilled things on the sample to check durability- so far so good. I know it will need touching up here and there, but the best part is, it is easily done. No more looking at scratches & stains in my polyurethane that I can't do anything about.

Is it more accurate to paint a poster board or wall sample? SwatchRight is a circle shaped paint peel and stick sample decal. The circle shape creates a different visual experience that makes choosing paint colors easier, your eye focuses differently on a circle than it does a square; physiologically a circle is more visually ergonomic than a square or a rectangle. You never view color in isolation. All you can do is manage the context. The existing wall color really isn't the issue. Everybody thinks it is, but it's not. Whether you're sampling on a white primed background or some other color, they both will influence your perception of the color sample. The only way to manage it is to engineer the test color into focus... and that's what SwatchRight does. Don't ever paint directly on the wall. Even with well-feathered edges, the sample spots can telegraph thru you final finish.

OOPS, I missed all these replies. I was running out of time so grabbed some foam core from Target and it worked much much better. Took two coats well. Still baffled that both Dill Pickle and Sweet Daphne aren't looking as "bright" as described even with good samples, but won't have time to search out any more colors at this point or paint anymore posterboard, so I'll just have to be prepared to not have exactly what I wanted. (I was a bit dissapointed with my local Benjamin Moore store yesterday. I took the samples in, plus stem green which I think is going to be way to bright and said "look, there has to be something inbetween Sweet Daphne/Dill Pickle (which is what they recommended when I asked for a cheerful (not neon) apple green) and this really bright stem green, what would you suggest"---and I got crickets. I've got tons of more muted greens painted up for my massage room so that should give me more choices for that. (I have chemical sensitiviites and got sick from painting the sample paint onto posterboard so I was down for the count several days and unable to keep searching for paint. My friend painted the posterbaords for me yesterday, but I don't think he'd be willing to do more at this point. I needed the new colors yesterday if I was going to have them, and didn't get much help at the store. My Ace hardware doesn't carry the peel and sticks in store. Someone else mentioned the drywall. I assumed I'd have to prime that. I found out after I bought the poster board that Benjamin Moore has large "posterboard" squares that feel like paper but are actually platic for $6 a piece that apparently are good for sample painting. The foam core from target actually worked much better than the previous posterboard attempts, so that was, at least, a success. Oh and the BM sample paints are all eggshell. But I will most likely be using flat. I wanted Matte, but Eco Spec only comes in flat, eggshell and semi gloss. And I need to use that paint due to my chemical sensitivities. OK, I think I answereed everyones comments! Thanks for weighing in. I've never hired someone to paint. I always painted myself and if a color was wrong just got more paint and started over. I am feeling the pressure of having to get this done right the first time but have run out of time. The painter I used had a color consultant I could hire, and I had an appointment booked with her but she only did Sherwin Williams or Hallman Lindsay and didn't have any input for Benjamin Moore paints. So I'm winging it. Luckily most of the house is going to be painted in a BM color I'm very familiar with with my old house. Still need an office, sewing room and massage paint though.