The guitar looks great!

Successful pot soldering does require a reasonable sized soldering iron with a widish tip. I now use two irons, one is temperature controlled soldering station and has a fine tip that I use for soldering all the small connections, and the other (a cheap 60W temperature controlled iron I bought from Amazon) with a wide tip, I use for back of pot stuff. It really makes a big difference and the pot and solder are heated up to melting point within a second, as opposed to six or seven with the smaller iron.