I have used hand sanitizer to get pitch out of Kuiu peloton 200 after using Google to find a solution. Worked great. As to the OP - I have had good luck with Nikwax tech wash or Dawn dish soap for oily stain.
I own the Alti mitts and have worn them making late season drives at -33F and had warm hands all day. You could also look at Hestra mittens. I haven’t worn them but have seen a lot of people use them on shows about Everest.