I am learning photoshop and created a custom brush tip. I had one picture open that I had doodled on, I then opened an new blank image and was able to draw pencil strokes on the image but for some reason when I try and use the brush tool it does not work. It only worked when I filled the blank image with a white fill using the bucket then I drew with the brush a doodle, was allowed to create a brush preset but then when I tried to use that brush it's icon appears on the image - the brush outline, but when I try and paint with it it does absolutely nothing. What the hell is going on I am obviously missing something really obvious? Many thanks.