Back to the smooth rear bumper again today

Right, I got a few coats of filler primer on, had me bowl of water and 600 grade wet and dry all ready to go and.........
........I found a bloody crack in the weld on the left hand side [

] It was only a little crack so I was able to sand the area back to the plastic then used my dremel type tool to grind a v along the crack and then re welded it, sand that down and then a touch of filler. All seems good now.
As it stands now I'm on my 2nd can of filler primer. Each can gives 3 good coats so I'm sanding after every can. One more coat from the 2nd can then some more wet sanding. Will got some pics of it later on once I'm done for the day.