As the saying goes, you need several arrows in your quiver.

Where you can blast to clean steel, epoxy primer is excellent.

Where you are making weld repairs, clean to steel first then apply weld through primer to the joint. Let it dry and weld away.

Where you have cleaned loose rust and paint but not all the way to white steel, a rust stop primer is excellent. I use Eastwood Rust encapsulator. I've heard good things about Rust Bullet. Red Rustoleum is good also; it just dries slow and you have to watch topcoating with a paint with "hot" solvent.

There are other approaches but the above has worked well for me. Eastwood sells most of the stuff I mentioned.

Do you have some pics of your project?