Depends.The speed you're driving at will determine how much load you're putting on your engine when you downshift. So if you're at a speed that would be high for the lower gear, then you need more revs to properly match. And for lower speeds, then less revs. It just depends. Experience will be the guiding factor for you. Just go out and downshift at different speeds while revving to about 4k rpm. You can tell whether you need more or less for the next time you're shifting at that speed into that particular gear. To downshift, just clutch, match revs, and downshift. No braking is needed unless you need the car to stop for the situation.