If all you want to do is make sure the rust doesn't continue to grow until you are ready to do a full restore. I would recommend you use POR-15. You can paint POR-15 directely on the rust and it will stop it cold. I would recommend you sand the areas of rust and try to get clean metal around the rust area then paint the POR-15 on it. Buy the smallest can I think that is a one pint or 1/2 pint can since it does not keep well once it is opened and it isn't cheap. One other thing make sure you use gloves and keep it off you skin because you will not be able to get it off once it drys for a few minutes.

You can find it on line or any good auto paint shop probably carries it. We use it on parts we provide to waste water treatment plants that have extremely agressive conditions towards steel and it is tough as nails.