Mica and grease is still in use today.
Like petrol, theres a reason its still used
Remove and clean the old mica insulators.
Grease can dry out, so a small 3 gram squeeze tube will be tons.
RS, E14, WES, Wagners, DigeyKey, Mouser, Altronics (their in WA)
Heck even PC shops will have little syringes of 'Goop'.
Do NOT use things like arctic silver as they are electrically conductive.
Thats the opposite of what you want