OK... I picked these responses because RIGHT OFF I figured you just HAD to have something mixed up. M26 is a wax, and it will feel totally different. M20 and especially M21 2.0 (both are sealants) have an oily type 'feel'. Not that it's a bad thing, especially after it cures.
I have topped M21 with a number of things and depending on WHAT and WHEN it gets various results. Bottom line is I'd let it cure overnight before topping it all the time for the best turnout and least amount of work. Streaks will happen sometimes, and MAY NOT be because M21 was too thick. Top it right away with another polymer product like Ultimate Wax (liquid or paste) and you'll see streaks, especially if it's liquid.

They WILL buff out, (on everything I've ever touched) but on black it's a PITA if you are trying to do it in a hurry. (Well let me take that back.... not in a hurry.... just doing it BEFORE YOU SHOULD!)
For ultimate wet sealant look.... top with ULW or the like. But pollen will stick to it like glue! Wait overnight for it to cure a bit, then top and it's not quite so 'oily'.
Make it a little 'crisper'... top with M26, and will feel a bit 'slicker' too. Don't have to wait overnight either.
As for the polishing oils causing a bit of problem. If that is happening, (streaking) then it's not a bad idea to hit it with IPA after polishing. Some will say just do it anyhow so you can see what swirls may be hiding in the fillers/oils, while others will say just leave it be and make sure you go THIN with the sealant.

Thin is in my friend!