I noticed a cheap propane heater rated for indoor use which made me think one would be great for the shop. as these are radiant heaters you just point them and they heat the immediate area , allowing you to pin point the Btu's.
Its basically a glorified camping heater , this one is for reference only as it's $118 , I bet they could be found for 1/2 the price, easily.
Dyna-Glo 18,000 BTU Propane Cabinet Gas Portable Heater-RA18LPDG - The Home Depot
This one is for indoor use apparently
Even a cheap Camping type would be good for those winter Projects
The above model is for outdoor use