Jackster is right. I got a large solder pot and made a "claw" out of galvanized thin steel to hold the board by the edges. I place all the through-hole parts and then dip the board at a slight angle, then make it flat on the surface of the solder, then tilt it the other way and slowly raise it from the solder. There is a bit of technique to have the lift angle and lift speed just right so you don't get solder icicles.
Oh, yes, I preheat the board on a 100 C hotplate for a few minutes before the dipping.
But, it works amazingly well.
Jon