I do both: for small fixes I solder by hand. Complete boards I usually use an old toaster oven, but often if the boards are really small, I use a soldering iron. I try not to go below 0805, but 0603 isn't hard.

I typically won't get a stencil for custom one-off jobs since they tend to be small and ordering them introduces delay. When I do, I use oshstencils.com. Had great luck with them and they are very price competitive.