Just sign-up for each as the sites you want to promote on
http://www.tushycash.com/join.html
So basically, if you want to promote strapon lesbians, you signup here:
http://www.tushycash.com/strjoin.html
If you want to promote tushylickers, you signup here
http://www.tushycash.com/tljoin.html
You can then merge all the accounts as you sign up (All CCBill sponsors, not just tushycash). So use the very first CCBill account you signed up with (Your master account) and put the details in the join form where it says:
"To load your current data, please enter your ID, username and password "
If you have never promoted a CCBill program, sign up with the 'create a new account' button..and then when you fill on the details for the SECOND site, use the method described above.
That way CCbill picks up the details from their database and you will get 1 combined check for all the ccbill sites you signed up for.
Hopefully that clarifies something :D