Ferg3333

You could add the GCS to the manifold. You then can turn off the diluent you are using(there will still be gas in the pipes) and then use the gas from the offboard bottle for wing inflate and dil addition. Although you gain very little doing this.

The main use for the GCS is addition via the adv. One end goes on the adv and the other part to the manifold, this way you can swap gases using the GCS if you run out of dil etc. Personally I would just put a normal buddy hose on the reg and then connect and disconnect underwater, with a flow stop on the adv.

Remember CCR is not like OC, it is recommended practice to keep the same dil throughout the dive.