Salt bath will not hurt at all, and the fins should bounce back very quick.
I wrote a how to on giving a salt bath http://www.bettafish.com/showthread.php?t=25297
- if you follow those directions everything will go smooth. The only thing you have to worry about is the 1st few seconds if he does not like that salt, he may try and jump out. some do, most don't and just settle in it and swim, just keep an eye on him.