I am thinking of doing this too, so I an NOT an expert you can rely on! A couple of useful things I have found though. Do not use a tin that has lead! Some say tin solder(without lead -- I ot one with no lead and a little silver -- rated for water systems) with flux is OK -- some not. There are videos on Youtube that seem helpful.

I bought a copper pan on ebay -- sold as solid copper. After a couple washings, the copper appears to be a wash over stainless even thogh the inside appears to have a tin coating. Any body seen this before?