my method for removing rodents has always been quick and absolute... I use d-Con poison, which after they eat a bit of it, causes them to leave by the same hole they came in.. then after a week or two, I search for, and plug all the holes to the exterior of the trailer so others cant get in...
I leave the d-Con blockes in nooks and crannies so its hidden and pets cant get to it, so that any rodents that may find their way in thru the door will be taken care of.
as for the BigHorn trailer that we have now, when I was installing a generator and transfer switch, I found an open hole at the end of the step frame, right in front of the entry steps.... they left it open to to run the wiring to the step lights.... but the mice had not found it yet... everything else is sealed by the corroplast.
as for plugging holes that are odd shaped and hard to cover, I find the easiest way is using epoxy resin, and mixing sand into it, then taking a piece of sponge or foam rubber large enough to fill the hole, saturating it in the epoxy sand mix, then wringing it out, and stuffing it in the hole.... when the epoxy sets, the sponge hardens and the rodents cant chew thru it due to the sand.... but as its not a super solid blockage, if it ever needs removed, it can easily be punched out and removed....
using regular spray foam can work also, but only if you take a zinc rich galvanize spray paint and give the sprayfoam a couple good coats after the foam dries....
ive used the rodent proof spray foam also, but only to plug holes that were a potential opening for rodents, so the rodents never had a chance to know it was a potential entry spot, and never tried to chew thru it..