What are you trying to achieve? There are so many ways and reasons to bleach (parts of) a print that it's not very feasible IMO to try and list every scenario.
Then there's the issue that each paper will respond differently to a bleach, with some requiring a strong concentration for a relatively long time compared to other papers which will bleach if you so much as look at them. How the paper is developed makes a difference, too, with slow, warm-tone development generally resulting in faster bleaching action than vigorous development in a neutral or cool-tone bleach.
The formulation of the bleach matters a lot; for instance, a ferricyanide + bromide bleach will be a lot slower than an irreversible Farmer's reducer bleach.
The general advice is to mix your bleach and then try it on a scrap piece of paper, for instance a test strip. When playing with bleaches and toners, it makes sense to print a couple of copies of the same image so you have a few spares to work on. Make sure whatever test strips/scraps you're using are properly fixed and washed! If you fail to completely wash the fixer from your paper, the bleaching action will be irreversible and faster, so not entirely representative for how the actual print will respond.
Try with a low concentration (1+100 or so) and mix it stronger is it's too slow to your taste.
Experiment lots. Have fun!
