I sometimes use a paint that stays sticky

but usually in 24-48 hours it dries hard. I don't like to wait that long but when you have to..............

I don't think sealing it would be a good idea.

Give it more time

testors dries faster.

Put it somewhere like a garage and leave it for at least another day.

Most people (me too!) rush paint drying.

Rustoleum takes a really long

Rustoleum takes a really long time to dry on models sometimes. I have painted a few hoppers oxide red primer and even when they finally felt dry they still smelled like fresh paint for a week.

Wait, and then ...

As long as you can smell

the paint on your model IT IS NOT DRY.  The solvent has to work it's way to the surface to evaporate.  With two coats of wet paint, this will take a pretty long time.  Maybe a couple of weeks.  If the paint job turned out good, DON'T mess with it.  Start working on another project.  This is the hardest thing any of us need to learn.

Temperature

Temperature of the room your item is drying in can have an effect also.  I've had items out in the garage that took long to dry and upon bringing them into the house, the drying went faster.  If it is too cool, the drying progress is retarded.

Dry and Cure

When finishing furniture I learned that after paint or clear finishes Dry, many take much longer to Cure. Some of the clear topcoats would dry in a few hours, but they took up to 30 days to cure. During that time they were releasing gasses. If you can smell the finish, it's not completely cured. When you're layering different products, you generally don't want to put something on top of a finish that hasn't Cured.

I also found that when I had trouble with something taking longer than normal to Dry, it was often a sign of old product.

gs