I suppose this is common knowledge,I clean lenses by first blowing and brushing with one of those gadgets made for camera lenses.After any possible grit is removed,I clean with alcohol,(rubbing),on a Q-tip.While hunting in the boondocks,this degrades to a hot breath and a wad of toilet paper.
I know better than to try and take a modern scope apart and haven't gotten the nerve up to do an early one.

Any secrets to removing stains on a Lyman slide, without abrasives?