Epoxy is not a primer. A larger tip would be for heavier bodied sandable primer. In the old days we used epoxy for a sealer with a little thinning and to protect bare metal .
Yup, of that I am aware. I use the term "primer" generically, but I know it is in fact, a sealer. I only know that because "My friend Pete" from "South West Rod and Customs", made a video in which he probably re-iterated the fact about 4 bajillion times. lol...