Use acid flux & melt/wick it off.
Use enough heat source as old tin/lead is a eutectic, but the newer tin/silver has a wide pasty range.
Put in a water heater a while back and used what they called "shark bite" connectors. They worked surprisingly well. Easy to use. Home Depot is where mine came from.
Do you have a propane torch? You can heat up the area with the solder and like dds said, use a rag to wipe it after heated up and it will be smooth and ready for a compression fitting.
Soldering is really not hard to do. Let us know if you want info on that.
Yep, clean the copper and flux the hell out of it works.
If you don't want a torch in the area maybe cut it off prior to the solder. Or use a baking sheet behind where you'd put the torch to stop the flames. I've done that before with no issues.
My problem is confined space and I just don't trust myself with a MAPP gas torch in the area. With soldering, I'm usually ok (flux the hell out of it).
Doc, that's brilliant! You're so smart, you should run a forum or something.
(Seriously though. That is a pretty friggin good idea.)
....I still prefer copper over pex.
.....
Congrats on getting that much fixed.
I still prefer copper over pex.
For the bread trick, it works good but be sure to take the aerator off of the facet when you turn it on so the bread can get right out of the system. Works like a charm.
what or where is the leak in the sink drain? Maybe we can help.