I've used Durabak in the past, here are a few of my learnings.
How to reduce cost:
Use the "indoor" version for base coat(s) and the "18" version for the final coat. There is a $35-40 price different per gallon. Although to ensure the final coat adheres well you need it to be a chemical bond. The final coat needs to be applied when previous coat is "tack free", tacky like masking tape but leaves no residue on your finger
Lite orange peel finish:
Use the "textured" version for the base coat and the "smooth" version for the final coat. This provide enough texture to greatly reduce surface prep and gets rid of the rough feel / dirt trapping of the standard textured finish.
I'll be applying some to a trailer I'm working on in the next week or so. I'll post some pictures of this type of finish when I'm done.
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Scott