Once wondering if there is a trick to brushing on the seam sealer?
Used the horse (?) hair HF ones first. Not real happy with the look.
Do/can you cut it with some sort thinner to get the factory look?

Dip the brush in acetone then brush the sealer into the cracks.

Lacquer thinner works. We call the brushes Acid brushes. They have a metal tube type handle.

Gotcha................
Should be able to find them at HD with the soldering stuff.
Thanks.

You can find those cheap brushes at the discount tool suppliers. Harbor Fright, Northern Tool, etc. You use them and toss them.