hmmmm...bridging is not really what you are looking for.

if you want to get the speakers in 2OHM, then do so. theres no special wiring needed. the amp will see the 2OHM resistance and change the power output accordingly. but you have to make sure that the amp will be able to take a 2OHM impedance.

to bride that amp:
you have this on the amp right now...

ch1 + -
ch2 + -
ch3 + -
ch4 + -

to bride that amp, you will use the + from ch1, and use the - from ch2 for one speaker. and do the same for ch3 and ch4.