My typical method for cleaning bronze/copper/brass stuff is below. Especially effective on cruddy coins.
I've yet to try the peroxide, will have to do that some day.
Preparations:
I make a saturated solution of ascorbic acid and water and put in a small spray bottle.
Also keep a small non-metallic bowl with (cold) water ready.
The cleaning:
Spray a little of the acid solution on the object to be cleaned, let it set
a few seconds.
In the meanwhile prepare a small bowl of water and add the sodium bicarbonate, ½ a teaspoon maximum.
Stir it a bit and immediately add the coin to be cleaned. Keep on close eye on it, unless the object requires several cleanings, the process is quite quick.
Crud is usually removed in well below a minute. Once the bubbling stops, remove and rinse under running water.
Repeat as needed.
Word of warning: If left unattended, the solution can eat up a nice patina.
Examples below:
Before cleaning:
First round: (this thick crud needed 2 runs)

Results:
