With the reflow thing (I'm new to soldering) I just hold the iron on the joint and feed some more solder? Is is possible to burn out any resisters or caps etc. if I hold the iron on too long.
Unless you find that a particular solder joint doesn't have enough solder to form a nice, conical joint, it's not usually necessary to apply more solder. Just "tin" your iron tip with a bit of fresh solder (this greatly improves heat transfer efficiency) and then touch it to the joint until the solder re-melts--generally takes only a second or two--and hold it there for maybe another couple of seconds. You won't damage anything as long as you keep the duration of contact in this range of just a few seconds. What this does is to improve the contact between the solder and the substrates in cases where the original joint integrity was low (a.k.a. a "cold" joint). As you gain more experience with soldering, these cold joints becomes less and less common, but for novices, poor joint quality is often the cause of issues such as the one you describe.
By the way, did you guys like my mighty mouse decal? And paint job? This project was super fun! Any recommendations on other good pedals to build? The od2 sounds fairly versatile.
The OD2 is an outstanding pedal--great flexibility. The FET PreAmp is another personal favorite. And (practically) every guitar player needs a good fuzz pedal, of which BYOC offers several.