As is typical, everyone comes in and tells you "dont dual mine".. the question was How to do it, not should he do it!
If you plan to use a raspi, get raspbian going (use google, there will be a few things to install to get cgminer going, works the same for cgminer dmaxl), then install from git
https://github.com/dmaxl/cgminer/Also make sure to install "screen" etc
Then, SSH in and run:
screen -dmS SHA256 var/www/cgminer --sha256 -o stratum+tcp://etc -u user -p pass -o --gridseed-options=baud=115200,freq=750,chips=5,modules=1,usefifo=0,btc=16
screen -dmS SCRYPT var/www/cgminer --scrypt -o stratum+tcp://etc -u user -p pass -o
Noting to of course change /var/www to wherever you build cgminer-dmaxl to.