So... Chose this awesome track by @dragondreams for the remix challenge. DD's version had piano sections, but I wanted to see what it'd be like without them. Apart from that, I tried to EQ things so that it sounded more metal rather than rock. Some of it came out blues, but that's fine.
Otherwise, I compressed the drums, added reverb to the bass and only synth I left in (deleted the others), and chorus to the vocals. Then just had to balance levels. I was considering adding some vocals, but decided against it.
2 things I would've done but couldn't - tame some of the cymbals (only had master drums to work with, not individual pieces); and tame the start of the final guitar solo (it was distorting in a nasty way, but controlling it ruined the rest of the solo).
All in all, I had a blast! Thanks @dragondreams!
Check out the original track here: https://fawm.org/songs/89679/