One quick question, in what position should the trailer tongue be when bleeding surge brakes? Extended or applied?

Level or up. The master cylinder should be the highest point of the brake system.

Applied, crack the bleeder and bleed fluid then close bleeder and then let off tongue. Repeat till no air. Topp off cylinder as you go so it won't get too low and allow air back into the system.

Don't even bother trying to gravity bleed. The lines run up from the axle to the wheel cylinder and would bleed hella slow if at all. Pressure bleed by yourself or manualy with two people.

On my trailer if you take a flat blade screw driver under neath you can stroke the piston and it has somthing that holds it applied for you. go back bleed one break caliper. then release it and do it all over again. takes a while and is a lot easier with two people.

I forgot to mention that I was planning on using a Mityvac hand held vacuum pump.

With MityVac you want it in the extended position...

If you bleed by hand it depends on whether you stoke the cylinder with a screwdriver, or you actually move the whole actuator with a lever (2x4 or similar). Either way, the actuator should eventually extend because of the spring contained inside. <BR> <BR>From everything I've read and from my experience it'll make it easier if your master cylinder is lower than the bleed ports, so air bubbles are forced upwards.