I'm wondering if there is any noticeable different with these 2 primers/undercoats. I'm assuming they are both high build ready for a top coat.
No idea about Hammerite rust beater or red oxide, but their Hammerite finish is not so good as it use to be, now using Rustoleum hammered finish & combi color. Could also look at Rustoleum CombiPrimer Anti-Rust Primer https://www.rust-oleum.eu/products/view/catalog/combiprimer-anti-rust-primer/
I've noticed with other threads too that Hammerite seems not to be as popular. I may well try Rust-Oleum