nice post
yes this is the way you are supose to properly fix a semi flex front bumper.
I go to a school called UTI.
I am currently takeing auto collision repair. we just recently learned on how to do this.
but the only thig that you didnt post was that when yo sand the cracked area, is that when you go and sand the inside of the crack you need to make sure you bevel each edge of the crack leaving no sharp edges.
if the sharp edges are left then the crack will eventually cut through the plastic compound and you will be doing this all over agian.
we learned using a two part compound made by 3M when you go and buy one of these products make sure you get a semi flex material or one that works with TPO plastics.
otherwise this is the correct way to fix theese front lips.
and on another side note put as much of this compound on the back of the crack and there is no need to sand the back side leave the bild up for more support.