I think you'd have been better off with a more concentrated solution but if it's working then fine. But instead of just letting it sit I've vigoroustly rubbed it with a rag or something else non abrasive on painted surfaces. If the solution is sufficiently strong this will pretty much remove the rust as quickly as solvent and scrubbing removes a stubborn tar stain. There shouldn't need to be a long soaking period. Or at least certainly no longer than a few minutes.

One the rust is gone and after a good rinse and dry you may be able to see the little pores in the paint where it bloomed out. Regardless of if you can see them or not the area should be sealed with something like a couple of coats of Danish oil or boiled linseed oil. These products are used with a wipe on/let soak/wipe off action so it soaks down into the pores and seals the rust. These types of oils dry after a while so they don't allow dust and grit to stick to them but you don't want to leave it on the outside of the finish since they do stay sticky for a while. A couple of applications wiped on and then the excess wiped off will be more than enough to soak in and coat the rust spots and seal them off from further problems.