Not too big a deal to remove the headliner on a golf as the hard part is removing it out of the car. Once you have the handles,screws etc off, the headliner moves forward [or backward ] where it attaches at the sunroof hole. Oh crap ,unless you have side curtain airbags.
Can you blow them through backwards with low air pressure. Just a thought, so not necessary to dissassembulate half the car. Cheers Dan
What I always did was take an air compressor hose, and a blower nozzle with a small tip, and go into the drains in the corners of the sunroof frame.(no worries of bumper removal, and cleaning the gook off my interior!)The front ones are easy to see in the corners with the sunroof rolled back, and the back ones may be unavailable with the headliner in, I am not 100%..If the seal is bad, junk will clog the drain.-Brad