Bumper smoothing advice

I put a post up the other day about bumper smoothing and advice on how to do it. I've done a bit of research and decided to make a start I have removed the black plastic strip then filled the holes with aluminum mesh and bumper filler. Half the bumper is body filled with all the holes re built I need to make the bumper level then ill be ready to rub down. Is this a good way of doing it that will last? I was going to try melting the plastic into the strip then skim it with body filler but thought this would be harder to do. Also with the rear bumper where the number plate sits on a 6n2 is that alright to fill or will that need plastic put in place?