How do you clean the years of "stuff", leaves, pine needles, etc. out of the cowl vent intakes aft of hood?

I pulled a small bird nest sized pile of Douglas fir needles out of one side, one needle at a time.

Where is water "supposed" to drain to? Engine bay like on 122?
Where does water end up if drain is clogged? Interior floor like 122?

How can I make sure the drain is clear?

My sun roof drains in A&C pillars were clogged too, dripping on head.

Thanks