Vinnie askes about modifing the coolant cap... This is not proven by
myself but I see no reason it won't work:

The cap on the reservoir is connected to the fill jug via a hose that
comes off easily.  Take the hose off and blow into the reservoir cap
nipple with whatever air source you have (limit yourself to 10 psi). 
There is a one-way valve in the cap, connected to this hose, so that
when the engine cools down the cap will allow coolant to be sucked in
from the fill jug with very little resistance.  Actually, the valve
is 2-way because if the coolant system pressure reaches the cap
pressure rating, it will purge coolant (there-by relieving pressure)
into the fill jug. 

I myself, prefer the breast-pump method... (sorry, old joke for old-timers 
on the list)