Good move filling the tank with water.
I don't solder professionally, but I have built a few computers, stereos, and fixed a couple radiators.
Most of your work is already, you should have a good tinning on the parts. I'd start by cleaning the excess solder off. Heat the parts up and wipe with an old rag. Cleaning the parts may let you get it started enough so you can wiggle it in with heat. Put a light coat of paste flux on and heat. Don't over heat you need just enough to keep the solder shinny. If your really good the solder will follow the flame. You may want to add just a touch more solder, you won't need much.
LG
