[suicideneil]

1) insert solder
2) insert iron
3) melt solder until it 2/3 fills the cup
4) insert pre-tinned wire
5) allow wire and cup to 'blend' together
6) withdraw iron
7) wait a few seconds for solder to solidify

Works for me- I just use lead-free sodler and my 45watt iron, no extra flux.