After draining the coolant out of a 2002 wrx, the new coolant/water mix is
going down very slowly, probably because the filler reservoir is connected
to the radiator via a very thin tube.

Now I fill the reservoir, wait a few minutes while the air burbs out of the
line and the coolant goes into the radiator, then fill the reservoir again.
At this rate, it could take days to put in 2 gallons.

Any ideas on how to make it go down faster? If there is another hole
somewhere on the radiator that I can open to let the air out, other than the
drain valve...