This is not something that easy to cure. Its not like you just buy some paint and hire someone to paint the rusted surface. No.
If its done like this, then it would be temporary solution only.
Preparation is the key. First you need to scrub that rust out completely upto the bare metal. Then need to wipe clean the surface with material like isopropyal alcohol (or you can use Thinner as replacement). Let the surface dry and then apply the paint.
Now for the paints, there is large variety available in market. You can find items from the range of pkr 300 to 5000. Technically any good coating will do the job. But there are coatings which are specially made for such type of situation (like above weblink shared). Find it and apply on the surface. If you are applying with paint brush, then usually single coat is more than enough (depending on the density of paint too or how much thinner/oil you mixed in it to make it thin). Making two coats with brush may reduce the life of coating. But if you are doing it with spray cans, then 3-coats are best with the time difference of 20-30 minutes as mentioned on the spray bottle.