"Jim, what do you use on your car's dash to protect it? I posted in the "interior" section, but never got a decent answer. I'm having "blotchy" patterns show up when I use Meguiar's Natural Shine (which works fine on tires, and does on my other cars' interiors...)."
For years,I only use Vinylnex by Lexol in my interior and all other plastic,rubber,etc.trim.
It is fantastic.Best I've ever tried.Here's a link to the product.
Sounds like you either have too much dressing product built up on your dash,or 2 incompatible dressing products applied one over the other which will cause the blotchiness look.
First I'd give the dash a good scrub/cleaning with any good all purpose cleaner.Always test a hidden spot first before taking it viewable.Then wipe it with a watered down damp micro fiber to get any poss remaining cleaning residue off.
A tip that I like to do when going for a good cleaning on the dash or other interior plastic trim,is to wrap a small scrub brush in a micro fiber soaked in the cleaner.It's effective and no messy drips.
Then put a generous application of Vinylex on and let it sit awhile.I like to put a second coat on and let it sit as well.Then I wipe it all down with a dry micro fiber and it looks evenly natural.
See pics below.good luck,Jim