When you get deep enough into it, you build your own reflow oven. I'm not sure (yet) if I will do enough of that for it to be worthwhile.
Daniel says to get a mask to apply solder paste and then stick it in the oven!
You can pay the companies that make the boards to get parts for you and solder them on. Daniel estimates $100 to do a 48 pin part. I can buy the parts for $7, so I could buy 7 of then and for half the price, make several tries. He says I might get by using the stencil and then my hot air rework station, but it would probably take some practice.
Tom's Electronics pages / tom@mmto.org