I just use this. If you always edit on the same machine you don’t have to create an account, I didn’t:
I don’t know how versed you are with image editing, but without trying to drown you in details:
After you have an image open:
- Create a new layer (+ sign over on the right next to base image)
- Paint THE LAYER black (big marker or paint brush on left)
- Set the transparency to 50% or so while you edit THE LAYER so you can see what you’re doing (click three dots way over on right on the layer for drop-down)
- Cut out sections from THE LAYER as you reveal (a Scissor button on left, be sure to select REMOVE)
Save and upload each iteration.