You may need to reload the brush with powder a second time. If the bristles of the brush feel scratchy on your face, you need more powder.
A blush or powder brush is best for removing excess powder. The size doesn’t matter as long as you’re using the right type of brush. If you’re not sure if you’ve removed all of the excess powder, take a selfie using the flash on your smartphone. Any loose powder will show up as white splotches on your face.
The water should be room temperature.
If you’re buying your own powder puff, look for one that’s about the size of your palm.