snoopy,
the Floquil primer works fine on metal with acrylic paint over it , i have never used Model master primer .
take some advice and you will save a few bucks, instead of useing Floquil, which is pricey try some automotive primer for metal figures. I have used it for years and it works as good as Floquil, and it is cheaper and you get more of it for the money.
and it is available at any hardware, auto parts store and wal-mart.