While I am not sure if I would want to fill swages in that manner myself (I have no sound reason for believing that though apart from I have never seen it done so am unsure of any reliability
history), on other fittings we use rigging
grade Lanacote instead of wax - warm the fitting with a hot air gun on a mild type temperature and the Lanacote will melt and run in. It then sets to a firm consistency.
On our own boat we use different rigging screws to most, they being an arrangement of telescoping threaded barrels rather than the traditional body with screws into each end, and these need to be protected in this way to prevent ingress of grit causing them to bind.