You really need to look in Scalehobbyist website. Tamiya rattle cans on sale for less than $5. Tamiya primer on sale for $5.19 each.
Hobbylinc are $7 for Tamiya primer and $5 plus change for Tamiya rattle can paints.
Either place you can’t go wrong. Just saying...
As far as Rustoleum primer goes, I have zero issues with them - especially the sandable primers. They have no grainy look and sprays really nice and smooth. Don’t get discouraged by Rustoleum. It has been my go-to primer for years. Now Krylon... I hate them and they’re pure garbage.