cleaning bronze

I did research on my family tree a few years back. Visited a lot of cemeteries and saw a lot of stones damaged, some from people who thought they were 'preserving'.
I think car wax would help to protect it, but do some real research (not on a car forum). There are a lot of cemetery / genealogy sites online that will offer cleaning methods. Just do a search, but you could try ancestry.com or findagrave.com I'm sure most will recommend the less you do the better, (prefering that you do nothing). ie. soft brushes, gently clean with mild soap. I would not try anything as aggressive as CLR, but if you do try to completly remove tarnish keep any chemicals off the stone or it could etch it with runs etc. Whatever you use, be sure to rinse thoroughly to stop the 'cleaning' process.