getting ready to paint the cab .that seam right below the back window realy bothers me .ive got it all cleaned out and its a crack i dont want it to rust as theres none there now. should it be seald and painted .or should i spray as much paint as i can get in it first. or just paint the body and hope enuff finds its way in .its kind of like drip rails trying to get enuff paint down in them that they hold up