The answer is insulate. Then you have a second decision to make. Are you going to rust your machines by having them below the dewpoint after bringing your moist breath in there, or are you going to maintain some heat all the time to protect them.
If you are going to protect them by keeping a bit of warmth there all the time, you can certainly consider convective slow heat like the electric, though at what cost, I don't know. Better for drying/keeping your wood dry as well.
If you're going to keep the place cold until you're in it or about to enter, then you want something that produces a lot of heat quickly and moves it mechanically to rapidly warm you and the things in your shop. Favors combustion on site and fans to do the job. Dust won't be a big worry around a flame unless you introduce a bolus of same by dumping the bag from your collector in proximity to the ignition source. When the concentration's low, it'll burn away with no problem. You'll of course want a furnace which filters air taken from inside or uses air from outside to avoid problems with oil spray or dust on freshly lit burners. Isolation in a positive pressure "closet" would be a reasonable choice, properly vented to handle fumes when you're not there, and the pressure generated.
Since you have, as I recall, a lot of trees available out there, you might want to consider the woodstove and ceiling fans option. Perhaps, if you're rural enough, one of those outside smokies located down the prevailing wind would be the ticket. They're capable of producing and storing a lot of heat in various configurations. Wouldn't be an economical choice for the shop alone, given the need to charge them up and the delay in obtaining heat, but I don't know the prevailing cordwood prices, nor if you can harvest your own.