Ed , the reason I mentioned the sandpaper is that Forest Mims III , who wrote all those helpful Radio Shack electrical do it yourself books said that most wire , even the fine multiwire we use on automobiles has lacquer on the individual wires in the bunch that makes up what we are calling one wire... and that for a good solder joint that needed to be removed... I do not think rosin based flux removes that and we sure don't want to use acid core solder for wiring joints... I expect some wire experts to jump in here and say that is not true about the fine wires... but the wires look physically much brighter, the same effect as taking off lacquer from copper in other instances and it is not going to hurt doing it... so I always do it. I think Mims says to use a match to burn off the lacquer from the ends....but then you would want to get the soot off so I just use the sandpaper to start with.
I have never run across any of the Shrink with Glue... but I am cheap and get my shrink tubing from computer stores in three foot sections,,, instead of from auto stores in those expensive packages ....
Another item that I have found useful for protecting solder joints is Liquid Electrical Tape... not as good as shrink ,,, but some hard to reach and/or temporary places I have used this with great success. Greg