Which Rusty Metal Product To Use ?

[Conaway2]

I’m reconditioning a pair of ‘29 running boards that have some surface rust on them. I’ve wire-brushed them pretty aggressively and treated them with Rustoleum Rust Reformer. I’m considering using either POR-15 or Rustoleum Rusty Metal Primer as the next step, but leaning toward POR-15 as it leaves a very tough polymeric coating when it dries.

What products have others used in a case like this where sandblasting is not readily available to me.

Thanks,
Jim