I use the copper foil on every guitar I build; it is far superior to any other option. Do make sure you solder all the seams together to guarantee good continuity. Make sure the bridge is properly connected as well. The very best practice is to terminate all grounds at only one point. Finally, test the installation by measuring the resistance from the amplifier end of the guitar/bass cable to the bridge/strings - it will be a good indication of a job well done.
I don't actually do that with the solder. The reason I don't is because when I test conductivity with a multi meter from many points and positions I get full conductivity. If I was using the tape without the conductive adhesive I would solder here and there. Just out of curiosity, how do you get your solder trails to stick? Any time I have soldered anything to copper tape it feels very weak and would just scrape off.
As far as terminating grounds, what I think you mean by this is remove all the wires that attach to the back of pots etc. I will do this. The trem had a wire going from it to one of the backs of the pots so I will remove that and attach it to an earthing screw that was already installed on this bass. In the main cavity the earthing screw had a wire run from one of rears of the pots to it so mechanically attaching the pots to the carbon paint in the control cavity.
What I will do is run the trem earth wire to this screw instead which is now screwed in and resting on the copper tape. The copper tape then connects all the way around creating connectivity. When the scratch plate is reinstalled and had the back completely covered by foil (I have a single sheet for this) it will make contact with the cavity foil because I have an area where the cavity foil comes up over the top of the body so it will touch the foil on it. For good measure I have an area where the foil from the cavity comes up onto the face of the bass and runs over a screw hole for the scratch plate. This will guarantee that the scratch plate gets screwed down tight and makes a connection with the foil below.
Basically everything then will be terminating at one single point because pots are screwed to the scratchplate which has the shield on it, the selector switch also, then then will all connect to the control and pick cavity shields which are all connected as one also. Both combined creates one single point.
I used to to the guitar nuts way and solder all to a single ring, star grounding I believe it is called, then I realised it was over kill!!!!!!!
If I plug in a cable and touch the earth and then touch the trem I will get connectivity with multimeter and the same goes for any other point I choose to put the multimeter.