Leaking when it rains? Where in the hell is this water coming from?

ok so more storms (been so wet in So Cal lately), more water on the floor. I removed the glove box and can see now at the upper edge, pinch weld I guess?, is rusty and has water trails. so that is where the cowl is meeting up with the side of the car? beneath the dash? How does one seal it? obviously cant go from the top, but not real sure how to get any sort of caulk or sealant in from the bottom either.
What about some of the putty epoxy stuff, it is like clay, would that be able to be wedged up there and stop the leak??
ideas? that dont require me to remove the dash