Another piece that works really well for cutting straight lines is a reciprocating tool, like the Fein Multi-master and it's clones. The circular blades cut through drywall like it's butter and it makes dust, but less than a Dremel. It doesn't have a dust collector attachment, though. The blades will become dull, but it will guide itself to a degree. I bought one from Harbor Freight and it has paid for itself many times. The blades are a lot less expensive than the ones from Fein, too.

The circular oscillating blades do a good job in plaster too. A few years ago we used a circular saw to cut a channel in plaster. Even though we constructed a tent there was dust everywhere and we looked like snowmen afterward. A few weeks ago we cut a similar channel with the oscillating tool, higher end vacuum cleaner closely chasing the blade, and no tent. Dust was not a problem. It is a good idea to wear hearing protection.

By the way the oscillating tool and straight blades do a good job cutting round holes in a plaster on metal lath ceiling. We used the diamond grit blades to get through the plaster and tungsten blades to cut the lath. Here we did use a tent and vacuum cleaner. We had excellent control over dust. The holes were nearly perfect.

I also have both the spiral saw(rotozip etc) and the oscillating saw. There is a time and place for both. In this case I prefer the rotozip due to mine having a vacuum attachment for dust collection, easier to precisely control the depth of cut, and the oversized foot makes tracing a straight line around a guide board very easy. In my opinion, the board trace method for long, narrow channels is the most professional. It gives a clean, straight channel, minimal risk of hitting something underneath, protects the removed sheetrock while off the wall, makes the final patch job easier due to the straight lines, and the patch screws being underneath the tape seams.

I never work with power tools without using my ear plugs- I carry them everywhere.

That metal screen lath is great. Really. I had to do the same and that stuff tore up the narrow steel blades, so I switched to using the corner of the carbide encrusted tweezers, er blade.

I have an old squirrel cage furnace blower that was at my parents' house after my dad passed and I put a motor on it- I'm going to make a spray booth/vapor removal system but it could be used just as easily for dust removal- get a piece of flexible duct, make a stand for it and run that outside, then have a wooden box with air filters for a furnace on each face, but make sure there's some kind of screen to prevent the filters blowing out, or under-pully the motor so the air volume isn't too high. Menard's sells a plastic sheet with threads in a diamond pattern, for strength- it would be fairly easy to make a wooden frame with that stretched across the wood, as an enclosed space for making a lot of dust.

I had to cut a new hole in the base molding of an older home last Summer and never thought of using a hole saw- just marked it for an Arlington LV-1 and made a nice clean opening. Then, the painter plugged it before he primed the trim. Yay.

Chalk line followed by a circular saw set to the a gnats hair deeper than the depth of the drywall.