Rain leaking into '95 Blazer

My brother and I are trying to figure out how rainwater is getting into my mother's '95 Blazer. She keeps ending up with a soaked carpet after a storm. It doesn't appear to be coming through the driver's door seal or around the windshield. We've cleaned out the area under the windshield wipers.

What strategies have helped others fix problems like this?

Have one of you sit in the truck while th other runs water from a hose around the seals, windows, ect...

Where ever it is the wettest, pull the carpet up. Dry off the metal as best you can. Buy some of the cheapest baby powder you can find and sprinkle it on the vertical surfaces. Then garden hose outside. Where ever water is getting in will leave a "slug" trail. A tip an old mech taught me many years ago. Also used for engine oil leaks etc.