Wrong forum sections but...
When I need to deep clean my watch, I use a soft bristled toothbrush. For the stubborn areas I add a wooden toothpick.
Moved to fenix 6 forum (was Connect iOS).
Isopropyl alcohol or contact cleaner on a cotton bud.
I clean both my watch and charger once a month this way, I also have a silicon cap to cover the port on the watch that I got from eBay