Mark,

whether you have self-adjusting rear brakes or not..
when you adjust brakes by hand by changing length of the rod between shoes
the centerizing of the shoes is far from optimum.  When you push pedal few
times shoes are self-centerized and you might have to adjust them more
tighter.

This is the case if everything is working proberly.  In case you have
self-adjusting brakes and you have swapped adjusting rods (from left to
right..) self-adjusting might work wrong direction (loosen).

You can hear self-adjusting working if you have someone pushing pedal while
you are by the wheel.  If the adjustment is too loose the mechanism tightens
when freeing pedal and there is audible 'click' at this moment coming from
inside the drum.

Hope this helps

Juha Koivisto
88 Vanagon (Caravelle) 1,6TD (old school bus with 9 seats)
TURKU, FINLAND