soldering

I have been soldering for almost 60 years, I was an electonics tech at the dawn of solid state. I learned from the best.
Three things are mandatory for consistant high quality connections.
1.) The surface must be clean. I have found that a micro wire brush works best. Flux has as many negatives as positives, the major issue is that it dirties the board and attracts buildup of corrosion.
2.) Use the right temperature for the job. A variable temp station is best, but in the "field" I carried a 100/150 gun for high temp jobs like heat syncs, a 40 watt iron for general duty (a 60w is ok also), and a 15 watt pencil iron for transistor and IC work.
3.) The correct solder. 60/40 resin core is a must!!!! Small diameter makes the job easier also.
Keeping the iron tip is important, but a dirty tip will still work with the right solder. I use copper or brass wire mesh (chore girl or boy pot and pan scrubbers work great and there're cheap). Also a good tight/firm wet sponge is a big help. The last and easiest tip (tip) is use tip tinner paste. I get mine from R&R Lotion Co. in Scottdale, Arizona, part# Tip-T. Their phone is 480-443-9255. It comes in a small tin for $5 or $6 but it lasts for years. Whenever the tip picks up any gunk just dip it briefly in the tinner and it looks and works like new. Great stuff!
I hope this will help some of you younger guys. Happy modeling!!!