Which of the following steps are specific to applying primer to avionic equipment?

The correct choice emphasizes the importance of masking all areas that should not be painted and ensuring that the item is kept in a dry and dust-free environment. These steps are vital in the application of primer to avionic equipment as they prevent contamination and ensure a clean surface for adhesion. Masking helps avoid overspray, which can lead to functional issues or aesthetic problems. Maintaining a dry and dust-free area is crucial, as moisture can cause premature corrosion and dust can lead to poor bonding of the primer, potentially compromising the protective qualities intended for the equipment.

While the other options include valid procedures, they may not be specifically tailored to the primer application process in the same way. For instance, removing rust and using a heat lamp for drying can be part of general surface preparation but do not specifically address the unique requirements for primer application. Other options contain steps that might also contribute to surface preparation but lack the critical aspect of preventing contamination during the actual priming process.