[Conquistador]

Not that it's of much use, but here is where the sunroof drain tubes run and what it looks like behind the roof panels (not mine btw).









As Del said, it's not the best idea to ram an arc welding rod down there like you're ramrodding a 17th century cannon, or even blow compressed air down the tubes. With the former, it's likely you'll pierce the rubber lines somewhere, and with the latter it's likely you'll rupture the brittle rubber, or blow the top of the rubber tube away from where it's secured.

I've used Del's method before, adapting a bug / chemical sprayer and using warm soapy water and it worked well.

Might be a good idea to check the bungs / drain tubes in the centre tunnel. You can find them in the central tunnel and peeling the carpet back a bit.