I borrowed a gun from my dad. He said he never could really get it to work right, and I think I know why. The guns aren't very good for doing detailed soldering. I ended up ordering a nice iron, and since then I've had no issues.
I've soldered up four batteries for the trucks, both ESCs on the trucks, and connectors to the chargers.
I've actually gotten quite a bit more proficient at it. It's definitely much easier with the iron than it was with the gun.
I actually enjoy soldering. It's kind of fun, in an odd "this is work, but it's not so bad" kind of way.
Tonight I did two batteries and one of the ESCs. Went pretty quickly, and came out perfect!!!