Can't answer about Rustoleum, never used it!
Generall most acrylics will go over most primers, but as ever, test it on something else first.
Primers in general have many functions, etching, rust prevention, prep for painting, etc.
For Modelling Purposes: It helps give a smooth uniform surface for further painting, especially if you are combining PE, Aluminium barrels, resin, or plastics in different colours.
Different brands have different properties.
A favourite is Acrylic Rattle-can primer from the Auto Shop/Car Factors. Available in Grey, white, (& no longer in black in the UK at least)
this has a lacquer/Cellulose smell, & bites into the plastic, aluminium, PE, fillers, etc.
This also can be further worked, filled, sanded, if needed.
Also useful on certain plastics, such as Fonderie Miniatures, which is the only thing I have found that will stick to it, & ally barrels.
Others use Vallejo Polyurethane Primer, needs to be sprayed, tough, but doesn't like being heavily sanded.
Others like straight black Vallejo black, or Humbrol Enamels, & others favour the black primer intended for the range of metallics by a company whose name escapes me at the moment!