And some contours with basic 1px brush.



Here we have it.



Now let's practice a little bit with new Alpha channels that are basically like masks.

Switch to channel box and tap on create a new layer icon in the bottom of the screen.
If you are now in channel box PS will create a new Alpha channel.



Use gradient:



Fill this are with black. Don't worry it will not affect your painting.

Switch again to layer box. And load the selection.



Chose Alpha 1.



And here we have it. See the Alphas act like masks and gradient overlay just defines the edges and further color of effect blending.