In my mind the coating has nothing to do with it.
You need a chunk of soft lead, maybe 0.004" larger than your bore, some good oil, a strong rod to push and hammer with, and a good micrometer (or excellent caliper).
I typically slug 9mm bores with 38 bullets that are the appropriate oversize, but not sure where to start for 45 cal. I've seen fishing weights discussed, but have no idea what sizes they come in.