WD40 is not a lubricant, sort of.
I have oiled motor shafts using full synthetic engine oils.
Advantage of synthetic is they do not burn-oxidize, dry up, so they last.
I would use a 5w-20 and drip it off a long tool-wire onto the shaft net to the bushing,
I found out about using synthetic oils on motors on computer fans. The fan bearings eventually dry up, even relubing with dino oils. But using synthetic oils, the fans don't dry up, I have years of proof that shows me this. Since then also other fan motors I have fixed using 100% synthetic oil.
There is friction in a bearing, even if it seems there is none. And over the long long time, regular greases - oils do a slow burn in the heat of a bearing. Synthetic oil is more resistant to heat, breaks down at higher temperatures.