From someone who lives in the cold -- the oil filled heaters are nice, but you need to leave them on for quite a while. The oil and metal all need to get up to temp before you really get anything out of them. Once they are, they produce decent heat and are quite economical power-wise. The small propane heaters that screw onto a 1lb bottle are often used for ice fishing up here. They won't warm that large of an area up, and a lot of the heat is radiant. An electric radiant heater would also be a good option. You can place it above you / near where you're working and aimed at you.
I had to do some deck work a while back, so I used the cold to my advantage. Mixed up warm epoxy so it would flow, introduced it to a cold boat so I could get it all where I wanted it without dealing with it kicking off, then left an oil-filled electric radiator running in the boat overnight.
That's a Catalina 22 over there somewhere.