I have been playing bass on and off for close to 15 years, but it has been more off than on and I was never really any good. Last year I bought an acoustic (six-string) guitar to try to get back into things. I learned some basic chords and scales, and then haven't practiced much until very recently. I really wish now that I had stuck with it, but I kept getting bogged down with work and family life. Anyhow, I'm giving it another go knowing full well that I should probably just hang it up as I ain't gettin any younger -- Here's my question: Ultimately I am most interested in playing death metal, but I'd like to learn the basics by playing clean on the acoustic (partly so I can hear my mistakes and partly because I don't have the cash to buy a new guitar right now). So what scales/progressions should I be working on? Any tips?
This seems to be one of those frequently asked questions. There's probably a sticky on it, but I'll give you a few.

Minor pentatonic
Major pentatonic
Relative minor
I am looking particularly for scales used in death metal, e.g. not the major scale -- and I guess I was looking for something slightly more exotic the the major and minor pentatonics -- Also, I am looking for general tips on what metal techniques will work on an acoustic and what wont. For example, is tremelo picking an "electric only" kind of thing? I am seriously considering selling my bass and amp (Hamer 5 String, Hartke head, 15" GK cab) so I can get a decent six string, but I want to be sure that I want to do that. So I want to stick with the acoustic for a while first. Finally, I am not a complete newbie. But in some ways I wish I was, because then I wouldn't have so many bad habits. Thanks. If there is a more appropriate place to ask these questions I will post there instead.