The reason why primer nozzles stay clearer is that their spray output has a larger diameter to accommodate the larger % of solids in the mix.

I never have these issues as I invert the can to blow out the nozzle and I dunk my nozzles in dope thinner after use. Dope thinner dissolves ALL paint residues (Lacquer, Dope, Enamel, Varnish, etc) other than 2-part (hardener-mix) Epoxy paint and 2-part (catalyzed) Automotive Urethane paint (Imron, etc), but neither of those types are being sprayed out of a rattle-can. 2-part epoxy and urethane paints are only able to be sprayed out of a gun or airbrush. Those must be cleaned when the paint in them is still WET by spraying them free of paint with thinner. If one lets those "harden in the gun" the gun is ruined forever .
The rattle-cans that are labeled "Appliance Epoxy" are a load of baloney. There is NO SUCH THING as a 1-part Epoxy paint. By definition that is an oxymoron, heavy on the MORON.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !