I guess I should have thought to point out that you need to consider your microwaves wattage. I use mine on low (hence the 30 second intervals). What has helped with the mattes and retro mattes I've melted so far has been to really smash them up until they are pretty creamy before I melt them....otherwise they are a pain in the butt to melt. I learned that from some trial and error though. I couldn't get All Fired Up to melt smooth at all or RiRi Boy but the others I went back and did came out ok.
The previous palette I posted after melting in the microwave (before they were melted with a hair dryer)
Orange & Coral palette
3rd from the top is the All Fired Up that refuses to melt smooth. RiRi Boy is directly below it.
Latest matte palette I started working on.