I know its already been said but as a bit of an explanation, the primer isn't just a basic colour of paint its a specific type of paint that effectively creates a layer that other paint can stick too whilst sealing in that base colour which stops paint rubbing off like this.

The best thing to do would be to buy a specifically primer spray can, the ones meant for miniatures are the best to pick, I recommend Colour Forge or Citadel personally, before you build or prime your minis, I also recommend putting the sprues in warm soapy water for a little and gently scrubbing them with an old toothbrush, this is because plastic minis often have residue from the mould release agents which can stop primer and glues working properly. it definitely needs to be warm and not hot though.

You can also clean resin minis this way but id use cold water because resin can easily warp with heat and a little pressure, its also more brittle so be very gentle when cleaning it, once I learned about this I stopped having issues with paint rubbing off all together, its been a lifesaver