Because melamine was specially crafted to resist kitchen spills like water, oil, and food, it does not take well to paint. Melamine also tends to be glossy (shiny), while Soto's Multi-Surface Paint Touch Up is matte (not glossy). We offer a Clear Touch Up in five levels of sheen, from matte to high-gloss, that can be used over our Multi-Surface Paint Touch Up. If you are trying to match a high-gloss finish, another option is Soto's High-Gloss Appliance + Porcelain Touch Up.
That said, a light sanding can remove the melamine surface (be careful you don't sand too much! -- you may also want to wear a mask and/or use a fan to avoid breathing in the dust), and then the surface underneath the melamine will accept the paint.
As always before painting, make sure the area is clean of all debris (dust, dirt, old paint, any oils or grease, etc., then wash the surface with soapy water and let it dry completely.
After painting, it will probably be dry to the touch within about half an hour, but it is best to let it dry for several hours before using it or adding a second coat. Let the paint dry for 1-2 weeks for maximum hardness and durability before subjecting it to heavy use (heavy scrubbing, putting heavy objects on it, etc.).