As others have sensibly pointed out, polish on matte is a bad idea, the surface of matte finish paint is filled with lots of tiny bumps which gives it the plush less-reflective finish, so applying a polish which is intended to smooth out bumps and scrapes is rather counter productive, and probably not very easy to remedy without damaging the finish.
I'll report back on window cleaner, I'm sure I've used a little with not much effect, but I didn't give it a thorough soaking first. I have matte red and black finish on my ebike, it has got oil drips on the top tube and forks from when I changed the brake fluid, which didn't want to come off with a little soapy water. It's very noticeable up close in the saddle, but hasn't really bothered me to the point of seeking matte specific cleaners, but the bike needs a good once over and I think I'll clean the frame up properly now. I never had a problem with oil marks on gloss paint before, so when I was about to put an order down on a matte black Trek Domane the other day and I mentioned my concerns to the sales assistant. I was conflicted about the viper red, it's not my taste, and the matte black looks like a stealth bomber, who wouldn't want that?! I mentioned my trouble keeping the ebike looking good, and the sales assistant assured me she had to wash matte frames down regularly for the shop, and with the right product it's no big deal. I don't think she was fibbing either, as there was a gloss option which wouldn't have resulted in a lost sale, there was no real reason for her to lie about it! I'm not one for expensive bottles of cleaner, so eager to see what a bit of elbow grease and window cleaner can achieve this weekend. If that fails, I'll maybe resort to a matte specific cleaner, maybe.
