I sometimes use spray silicone on cotton threads if they tend to break or shred, mainly on the quilting machine. Doesn't hurt a thing
I do this as well - especially for threads that I am having problems with on the longarm. I however just apply a short light spray down one side. I expect the end result is the same as using Sewers Aid (who's directions Ithink says apply one drop) Both products would act as a lubricant. My only concern is that dunking the whole spool in may be too much of a good thing.