what I do is modifying follow 2 files.
in /etc/config/cgminer, add --load-balance into more_options
option more_options '--quiet --load-balance'
in /etc/init.d/cgminer, add $_mo into PARAMS
PARAMS="$AOPTIONS $POOL1 $POOL2 $POOL3 $_pb $_mo --api-allow $_aa --api-listen"
add your pool in webui, apply change. then happy multi-mining.