Indeed. Quick and dirty old school shortcuts like these should only be used by experienced people who understand exactly what they're doing. Even then they're bad practice.
To inject tone into RF and AF stages you can use a basic two transistor signal injector. These make excellent constructional projects for beginners. None of the components are critical so they can be built with bits from scrap equipment.
http://www.eleccircuit.com/simple-si...by-transistor/