Good luck keep us posted.
The first thing you need to do is wash it to remove the chalk that is there and you can do this with a combunation of power washing and hand washing with a brush. If there is a Duron paint store in your area they will have a cleaner called house and deck wash by MITM and that will do a good job of cleaning your the siding. After washing and hopefully all or most of the chalk came off you will need to prime with Duron Siding in a Can acrylic primer and then finish with Duron Siding in a Can satin or semi-gloss acrylic coating. If all of the existing coating comes off down to the bare metal you will need to prime with Duron Dura-Clad White Alkyd metal primer and finish with the same products above.