That can be a lot of fun, Don. I've found one of the best 'blackener's for the front sight glare, as well as rear sight, is a dry-erase felt pen. If you touch the sight as in when loading, just touch it with the felt pen and it's dull black again. I find the permanent felt pens suck due to shiny finish, however the dry erase are dull. The spray can of sight blackener like Birchwood Casey's is also good, but the felt pens much cheaper and quick to use. As well, they take up little room in the possible's bag.
Dry Erase Pens for sight blackening.