Mineral spirits, and other solvents, dissolve lube and allow the debris suspended in it the be removed more easily.
You do not have to put lube on a needle It is a method to apply a small amount of lube. You can apply directly from the bottle, but you will most likely end up applying ALOT of lube, which will make your yoyo rather responsive and, can leak out onto the axle and response system,causing issues with performance.
It is too early in the morning for me to be able to tackle the rust question.
You can apply straight from the bottle. It won’t really do anything to anything on the yoyo. I do it that way all the time because I’m too lazy to try to find a needle. Haha.
The only way you could remove rust is to find a chemical (not sure which one it is) that can basically de-oxidize it. Most people on this forum won’t be able to do that.
1 mineral spirts cleanes out all the lube, residue and stray particles in the bearing causing it to run smooth have greater sleep times.
2 you can clean a small bearing with the same method. just remove all the shields and c clips from the bearing like you would with a large bearing.
3 you do not need 1 drop from a needle. that method is prefered to add a small perfect amount of lube to the bearing. you can add lube from the bottle but it will come out in a big drop as well as fast as thin lube has the consistency very similar to water. if you do not have a needle how did you clean the bearing in the first place removing the c clips and shields. you can clean it with those things on but it is not guarenteed that all the particles will come out.
4 to remove the rust from the bearings you would need a cleaner to clean the oxide from the bearing that might potentially hurt the bearing. you could also go to a jewlery store and ask them if you could use the thing they use to clean the jewlery thru vibrations. however you should take a large batch of your bearings so your not wasting money on 1 bearing. if you do this you should suspend the bearing in the mineral spirts.
5 to take care of your bearings in yoyos do not keep string on for a long period of time. keep your yoyos in a cool dry place. humidity is BAD. always lube your bearings in a small amount after cleaning. and allow your bearings to break in and do not always just clean them
what im doing is soaking it in kroil for 2 days 1 day on one siade 1 day on the other and ill give it a good cleaning after that and ill see the resultsss btw its a yyj bearing