Where IS the drain, so I can get ahead of this and rod it out?
Roll back the sunroof completely, and then undo the 2 small leashes that hold the popup sunroof wind deflector up and then fold the deflector back towards the rear. With a light, look into the VERY front corner on each side, and you will see a SMALL (<1/4") OVAL hole, split by a small, curved metal "gutter" that direct any water into the drain hole. Since the hole is recessed and oval, it is VERY difficult to get a rubber tipped air gun in there to seal well, but with a long rubber tipped extension, it can be done. The hose drains out through the wheel well behind some wiring on the DS, and underneath the glove box on the PS.
If necessary, and with some minor panel removals, and major arm contortions, you can pull the tube out from the body grommet on each side under the dash and blow air back up towards the sunroof and then out everything back together. It SHOULD be simpler to blow DOWN through the corner holes…you can hear the air rushing out by the wheel wells.
I found a link to a pic that shows the tube under the dash…I will try to post it back here.