Is ONR version 6 okay to use on matte paint?

ONR version 6 is absolutely safe for matte finishes and will not change the look of your paint. The reason people worry about wax buildup is because many traditional waxes or synthetic sealants are designed specifically to introduce a high degree of gloss and hydrophobic slickness, but ONR's purpose is a pH neutral cleaner that focuses on lifting surface contaminants and provides a protective layer without adding any optical shine or slick film.

For maintenance use, diluting it in a spray bottle is exactly the right move. Since you are only doing quick wipes to remove road grime and splash, you are not using it as a full contact wash, wich is much gentler on the finish. You don't need the whole two-bucket method when you are simply misting and wiping down dirt, but you do need to be careful with your technique to prevent scratches from grit. Always start with the least contaminated area, like the hood, and work downward. When using it on a matte vehicle, the biggest threat isn't the cleaner itself; it's the abrasive nature of road dirt and salt, expecially when it's freezing or damp. Because you are using it every other day, focusing on quick decontamination is smart. Just make sure you rinse the application area with a small amount of clean water before wiping, particularly if you notice heavy road film. Keep an eye on your spray bottle to ensure the dilution ratio is correct. While the concentrated version is fine for testing, using too much in a maintenance spray can lead to unnecessary residue, even though ONR is designed to rinse clean. Just a light, fine mist is all you need for touch-ups.

I went through this with my matte gray crossover last winter. What actually saved me was the towels, not the spray. I use a big pile of cheap microfibers and grab a fresh one for each panel, folding to a clean side constantly. The one time I reused a dirty towel I ended up with these faint swirl marks that only show in direct sun, which matte paint apparently shows more than I expected. Does the cloth itself matter as much as the wash stuff does on a flat finish?

I'd push back on the idea that misting and wiping every other day is gentler than a real wash. On paper maybe, but in practice you're dragging a towel over dirty paint with barely any lubrication, and that's exactly how flat finishes get burnished shiny in spots. I did this on my old wrapped hood and wound up with a glossy patch right where I wiped most often. A proper rinse or foam first, then ONR as a spot clean, beats constant dry wipe downs. Also, that 'protective layer without shine' claim sounds optimistic to me, polymers are polymers, test a small area first.