Make sure your revolver is unloaded.
With the action closed, point it in a safe direction.
Pull back the hammer.
Place a pencil between the hammer and the frame of the revolver.
Pull the trigger, letting the hammer fall on the pencil (not the firing pin), but do not release tension on the trigger. Keep your finger on the trigger pulled back in full firing position.
Grasp the cylinder in your other hand and try to move it back and forth to check the endplay between the cylinder and the barrel. If you have a feeler gauge you can check the gap between the two more precisely.
If it is out of spec, a gunsmith may be able to shim the gap and reduce powder flash from the cylinder.
Don't know of any purported low-flash powder offhand but I am happy with W-231 for "lower" flash ammo. I don't have any problems with its burn characteristic.