You need decent silver solder for motors and ESC I use
this stuff, expensive but brilliant.
Soldering irons need to be able to keep the joint supplied with heat so higher power is better typically. Soldering stations have decent power supplies that can control the heat well and I use one for small scale electronics. For RC racing I have an amazing gas powered iron which is rated at 125W but is controllable and has interchangable bits and can be converted to a hot air gun for heat shrink tubing.
This is the kit I have, it is great value and has soldered 1/8th scale electrics. The make - Portasol - is the daddy of gas irons and they OEM for Snap On, Antex and a few other brands as well.
ebay link
All that and it is portable and can travel to the track with you!