all about heat transfer, clean iron, flux. those and practice.
If your Iron is crap.. go get a new one - if your tip is replaceable replace it. if its black or nasty get a new one!
A good iron should be able to heat your component quickly so you can tap your solder to the component.. you dont heat solder then jab it so it sticks to things.
The flux in solder will help it flow.. but if you preflux your solder surface its a good help to know when its hot.. when flux bubbles away tap your solder.. practice.. when your good solder will just suck right into the part.. super fast and easy.
pop bumpers do stink, a good small solder gun helps you can get right in there, Frys sells good small ones under 20 bucks. also handy to pick up a 2$ desoldering gun there as well .. they are a lifesaver if you make a mess.
if you make a mess DONT BREAK IT OFF, DONT SCRAPE IT OFF. let it cool. go walk around.. soldering under stress causes bad things to happen.. a desoldering gun or bulb costs 2-5 bucks.. GO BUY ONE.. come back heat up the mess and click the desoldering tip on the mess.. mess go bye-bye!
if you solder too much jumper pins etc that sholdnt be.. add a little flux to your tip .. make sure its clean and hot.. then use a desolder gun to just suck it right off when its hot.
I personally dont like to add wire to pop bumpers (the metal ribbon) but that is also an option if your stuck.. another thing I have done is used grounding strap (like used in pinball machines) in a pinch ..if when the pop bumper was pulled you simply cant attach the ends of the wire back together, use that ground strapping and just extend it a bit.
also when you cut out the pop bumper wires... measure 2x cut once.. pre plan how you put it back together.. will your solder iron fit.. can you easily re-assemble the wires with little or no effort if you just moved a inch the other way.. can you pull staples and then get to it rather then cut it at the "pain point"
rather then fixing it like a car that needs to run to get to work.. fix it like a classic car you expect to have running in 4 years. that way you dont rush and dont make mistakes that cost more down the road. (or make someone buying your pin say.. WTF this is a hack job!)