Solaris 10 is easy, because the mpxio capability is built-in. You just need to turn it on!
To enable it, edit the file /kernel/drv/fp.conf file. At the end it should say:
Just change yes to no and it will be enabled:
Now this turns on mpxio for all fiber channel, if you are running internal FC drives do this in the same file:
name="fp" parent="/pci@8,600000/SUNW,qlc@2" port=0 mpxio-disable="yes";
you get the parent info by doing an ls -ls on the /dev/dsk/c0t0d0s2 file (or what ever your internal disk is)