Change the Fill Opacity on the fly
You probably know that (with a non-painting tool selected) you can press a number to change the opacity of a layer (1 for 10%, 2 for 20%, etc.). But what if you want to change the Fill opacity rather than the opacity? Add in the Shift key, pressing Shift-1 for 10%, Shift-2 for 20%, etc.
I’ve always wondered – What’s the difference between Fill and Layer opacity? Yes, I’m an amateur, but I can’t tell the difference for anything I’ve done.
To see the difference, try adding some effects on your layer, for example Stroke effect, and change opacity, then change fill. Changing opacity will affect the layer and the effects, while changing fill will affect only layer, not the effects. Try this with Gradient Fill effect also.