The real caustic type of paint remover is great at disolving dried up sew-up glue. Any sticky residue can be cleaned up with acetone. Use gloves and lots of ventilation, because both of these things are nasty. Don't put a huge amount on or you'll get globs of caustic brown snot in the spoke holes. Flush with lots of water when done.
Don't try this with foil wrapped balsa wood rims!
I cleaned up a couple of rims last week and found two loose washers inside!
Leonard Bulger
Ann Arbor, MI