My approach was more or less the same as Rduke. The one exception was that I raptor lined the interior floor panel before bodywork. It is next to impossible to get it as clean as it was when it was first done thanks to the filler/poly dust. I suspect the same would happen to the underbody if you raptor lined(or similar) before the weeks/months of making things dusty.

Thanks all,
I will wait. I live in northern Colorado so we don't get much humidity.

We do it in the opposite fashion. We do all of our floor prep and repair as well as our upper repairs, then go to epoxy. After epoxy , we seam seal all of our panels and complete our upper end and lower end bodywork. We perform all of the subsequent primer layers and blocking, go to paint, then Raptor line the bottom, then cut and rub the top. The reason we do this is twofold. 1- you can't tape on undercoating for a damn but you can mask on cured paint perfectly, and 2- you can't get overspray off of Raptor liner to save your life- you can only reapply it and spot it in. We paint about 15 Bronco bodies a year and ship them worldwide and this is how each is done. I have one customer who insisted he Raptor the bottom first, then did his body and paint and he regretted it. You just can't get all of that dust and overspray off of that high texture finish. Just my 2 cents. I'll be doing all three of my cars in this manor as well.

The SEM urethane bedliner I use has a gloss finish. Tape sticks and it cleans up easily. A little different than conventional bedliner but great for what I use it for.

Not a fan of Raptor for just the reasons you listed. Attracts and holds dirt.
Don

To each his own I suppose. I like their seam sealer but not their bedliner stuff in this application. Just not as durable and crisp looking as Raptor IMO. The point is that it's applied after paint at our shop. We feel it gives us the best results and the most crisp lines and edges.