hmmm, now im stuck in two methods, one leaves the bumper trims in, and the other has the out.
with the bumper trims in you would have to layer over them and fill the gaps with loads of fibre glass rammed in. thu building a profile higher than the rest of the bumper.
which then means you'll have to sand it back down until flush.
method two, without bumper trims, means you will have to use some plastic behind the fibre glass to raise the level abit. ( ie, peice of plastic with mulitple fibre layers ontop until flush with the rest of bumper. )
as for application, generally it will stick to anything with the fibreglass resin cement. but using a ruff gritt sand paper on the contacting surfaces before hand will help adhesion. ( sp)
build the layers up bit by bit, to much at once will make it sink. say 2 layers to start, let it harden, ruff that up with sand paper, then add a few more layers. when you are vertually ' level ' with the other apposed surfaces of bumper, use a filler to skimm over and flat down. ( to fill any slight low spots or crevises) once thats done, spray primmer on , and then using a cheap s**t paint dust that over so it looks like splodges and sand again with 1500 til the paint spodges have gone, and finish off with 2000/ 2500 gritt to smooth surface. paint, laquer, 2500 wet flat back, compound back upto a shine and done