I tried "Add a Pixel Layer" that didn't work. I then thought it would work if I duplicated the layer. Layers are created but there is nothing I can do on them. The brush settings do not matter, I have tried changing them. Do I open a layer, then select the brush tool. I tried this, but it did not work either. I started by duplicating the background layer then proceeding to clean up the image which worked fine. I then opened a pixel layer and tried to use the paint brush on some areas, but from this point, I can do no more adjustments on the image, whether I open a new pixel layer or duplicate the layer. I really cannot understand why! I did the same in GIMP and it worked just fine. Maybe in Affinity the procedure is different.