You don't need to boil. Put the chain in a plastic jar or jug with some soapy water and shake shake shake. Rinse and repeat, remove and pat dry, then dunk in the new hot wax.
Agitation removes everything. If you have any doubt, clean an old chain with this method and then pull the links apart to see what's inside. I did a few times before settling on my method. I don't think rust is going to be an issue, IME the chain needs to be almost completely dry before the oxidizing can take place. In the span of cleaning to re-waxing rust is not able to form.
FWIW I did not find much cleaning effect from plain water. You don't need a solvent but a surfactant helps.
Last edited by Spoonrobot; 11-07-19 at 10:09 PM.