I do mine myself using Hydrosilex brand products. Can get the whole car done in less than 20 minutes and I do it once a year. Sure it’s not a professional ceramic coating, but it works. One bottle was around $75 and I can get about 6 uses out of it.As others have said, gray is one of the best colors for not showing just how dirty it really is.
Off topic a little, as said above I had ceramic coating professionally applied to my white 22 LmtXT. Hope the products works well as it was a bit expensive.