Sometimes soap on a suspect area will find a leak also. It may take awhile on a very slow leak, but suds it up, and come back 30 minutes later and you may have a spot of white foam there. Also any areas that look oily is a spot where it has been leaking for awhile.
Exactly what I ended up doing was replacing parts with any leaks(oily spots or soap bubbles) also put some dye in when I charged it just in case I missed something.