Flathead pre-oiler - good, bad and the ugly?

[V8 Bob]

Ziggster,
You would be better starting off with a clean pressure vessel, like an inexpensive common garden sprayer, vs one containing "crud/rust". Using a filter is a good, but a standard full flow would allow much higher volume, important when pre-oiling.
Pictured is the one I use on my remote-filtered flatheads and BBFE during initial fresh build start-ups, and regular oil changes.