keep in mind that there are different types of seam sealers. Some stay softer then others and some cannot be painted over. Just explain what you want it for and they should be able to supply you with the right one.
3M makes a product in a tube called "drip-check". dries hard like the original yet still somewhat flexible. make sure your painter knows you used it, i have heard of some problems with certain brands of paint adhering to it.