I don't really use cupramine much anymore. I use chelated copper and I feed medicated food during copper all the time without issue. I would not combine general cure with copper unless its an emergency (if you are talking about dosing the water, adding it to food with focus is fine during copper) I would wait until copper treatment is complete and the water is copper free, then move on to using GC or prazipro.
Praziquantel is very hard on the available oxygen in the aquarium so with the reduction of oxygen plus the immune system suppression from copper I would advise against it unless you have a fluke infestation that is becoming lethal. Even then you can use FW dips for relief until copper is complete. Prazi+Copper can also result in nasty bacterial blooms further reducing the available oxygen in the aquarium causing major issues.