Forgive me for stating what should be obvious, but conductive shield (done properly) is an application of science . . . too often done by people who sorely lack understanding. People who casually state things like "works just as good" almost universally have only an assumption, and do not have any technical measurements or similar performance assessments.
THINGS YOU SHOULD KNOW:
1. By its very design, it is impossible for a guitar to ever have a 100% Farraday cage. Penetrations in "the cage" for pickups, pots, etc. require penetrations that allow (minor) electrical interference to enter. Any issues from this are extremely minimal; however, this needs to be understood.
2. Every type of metal has a unique set of characteristics, including an ability to be conductive. Copper is vastly superior to aluminum - in fact, most building codes ban aluminum wiring because of its shortcomings. Household "tin foil" or HVAC aluminum tape are not recommended. (Again, aluminum is the least desirable material. Tin foil lacks conductive adhesive and is ridiculously flimsy. HVAC tape thickness creates an undesirable height gap between the pickguard and body.)
3. Any electrical circuit requires continuity which means that every element MUST have a good connection to other components. Tape without conductive adhesives are simply not made for conductive shielding - soldering laps is perhaps a satisfactory workaround but it inferior to doing it correctly with tape that does have conductive adhesive.
4. Combining copper shielding tape and conductive shielding paint is acceptable. Paint is preferred for rough areas such as wood in a body cavity, whereas tape is preferred for smooth/slick surfaces such as plastic guards. You can use shielding paint on plastic but you may experience adhesion problems. If you want to paint plastic you should first clean it and apply a thin coat of primer.
5. It is absolutely essential to use a grounding lug/grounding wire for a conductive shielding system to work.
6. Shielding tape on the back of pickguards and cover plates (when installed) must have a solid contact (connection) to the body cavity shielding. A common way to do this is to extend the body cavity shielding (paint or tape) outside of and around the perimeter of the cavity by approximately 1/8" or so. (make certain to not extend the shielding to a point that will not be covered when the pickguard or cover is installed.
Cutting corners may allow you to save a few bucks and maybe think you're smart, but the end result will not provide the desired result. If you're going to invest the time and want a quality result you should always use the best possible materials and quality workmanship.