Yes, spraying paint gets more coverage faster, but when ya factor in the overspray prepararion and cleanup on subjects where ya only need a good long lasting coating and esthetics are not a priority, foam brushes are hard to beat. Foam brushes do have limitations, but as described this is work being done outside on an old utility trailer with bare metal showing from recent welding repairs, less than ideal conditions on something that is seen as an implement, not a show piece. Weather conditions should be improving when I get to the fenders, so I plan on doing some wet sanding to induce some shine, but the rest of the trailer I'm only trying to keep a smooth finish as this thing will get crawled over and beat on by ppl usually in a hurry to get a chore done.
The propane tank painting experiment has proven that using these economical methods outdoors works well as ideal working conditions are limited and the need to complete projects with adequate paint finishes overrules the need for superior paint finish results. My collection of Purdy brushes has served me well over the last 15yrs, and they do great on woodwork and sheetrock, as long as it is not too windy. I had to trash one of my Purdy brushes years ago cuz I tried to finish painting an eave as a storm system popped up and was blowing in...apparently the paint dried on the bristles on the last few sq ft and while I tried to clean that water base paint off, it was clear that the bristles were purt'near stiff as a board and nothing I tried could recondition them...lesson learned.