Only that the StewMac shielding paint is easier to work with in the body cavity. Why? Because every piece of copper tape you lay down has its bottom side coated with adhesive - with me? Which means that every single overlay needs to be soldered to the piece it touches - laying it on top of the piece does not make electrical contact.
One workaround is to do the pickguard and then run the tape in the body cavity up over the side of the cavity. That way when you drop the pickguard on, it will touch the face of the copper in the cavities. And this is a lot of work really but you might enjoy the time spent, I don't know.
If you use the paint, remember to use a screw and a lug (like Fender does) to attach a ground wire to the pots.
To be effective, all pieces of copper tape should have continuity to the guitar's ground...so you may have to solder the pieces of copper tape together. You can check the ground continuity with a DVM set to the lowest resistance range and all shielding should read very close to 0 ohms between all shielding and the guitar's common ground point (usually the volume pot shell).
Also, due to the extra stray capacitance the shielding adds, you may experience a change in tone...most likely some loss of the top end sparkle...which could be a good or bad thing .