The drain holes should be either in all 4 corners, accessable from the top-outside. Yeah, you could see them from above the headliner but THAT'S TOO MUCH WORK.
Take a blower nozzel and whit the sunroof open, blow around the corners where the seal of the glass rests when closed, and look for small (3/8"+) openings. 'Gently' dig around with a small screwdriver if there is crap that isn't blown away. And then blow the compressed air down them.
You gotta use common sense now.. If it's clogged enough where it won't blow, use a plastic line/hose to poke in there. They are held on by clamps similar to the other ones Honda uses but are of less tension and have longer 'legs'?, so you might blow them/pry them off.. Then you WILL have to pull the headliner.
Another Cheap way to make a better seal is to pull the glass out. Gently do the same with the seal around them and then just lightly push the seal/weatherstripping back on, letting the force of the power window do the rest.
This way, the seals sticks up/out just a little bit more taking up any previous irregularities. This works easily on door/window seals too, and stops wind noise.
OH, and get a can of Silicone spray and mist over the seals when finished. Use the 'jet nozzel' with window down, and spray into the channel of the window rubbers that guide the glass up and down. It WILL save wear and tear on the motor/your arm. If the glass is tinted, it's easily cleaned off without damage.
Sorry for not replying sooner.
E