Magnetic Paint phased plan
Step 1:

Choose a smooth surface where the magnets are to go, in a children’s room for example.
Step 2:

Stir the paint thoroughly and apply a minimum two or more coats. The more coats, the greater the force of attraction.
Step 3:

Allow each coat to dry for a minimum of 3 hours.
Step 4:

After 24 hours you can overpaint the wall in whatever colour you want.
Step 5:

Done! When the paint is completely dry the wall is suitable for any magnetic object.
Step 6:

No more drawing pins or adhesive tape on the wall, just the posters, photos, drawings, etc, held up by magnets.