From what I've learned recently that there's this really great mechanical rotary attachment made by 3M that can really get off gasket material safely without damaging aluminum. It's specifically designed for automotive gasket removal one of which is dedicated for aluminum, the white disc
This fella here walks through the white, yellow, and green discs, which increase in roughness as you go up. Here's the relevant quote from his video, and here's where he's using the tool, the white disc on a cast iron engine block's head surface...
Now what I use is these 3M Roloc Bristle Discs, and they're the best
option out there as far as removing gasket material quickly and
safely. Now they do produce grit just like any other abrasive so you
need to be careful with the grit and where it goes. But there is
different grits as far as how aggressive they are. It goes from 50
grit green, to 80 grit yellow, to 120 grit white. Now what Ford
recommends is to use the green on the actual cast iron surfaces and to
use the white on aluminum surfaces.
Here's another use, this time of the yellow 3M Roloc bristle brush on an aluminum head. He refers to the disc as a metal safe cookie wheel. He also does the same treatment to the throttle body mount to the intake manifold just shortly after the above.
There's also chemical means like the CRC 05021 Technician Grade Gasket Remover which I've read you use a special plastic knife with after the chemical spray softens up the residual gasket material.