I've successfully used the Bintel EP cleaning solution (only for very old/grubby eyepieces), but you need to use sparingly and avoid leaving any behind to dry ... or else you will get a residue.
A lens pen works well for me aslo (for the occassional bad fingerprint).
https://www.bintelshop.com.au/Product.aspx?ID=6621
I've also learned to put the dust caps back on my EPs when not in use ... avoids most dust and foam/lint from getting on the glass in the first place.
