Follow the manufacturers instructions.
I've had 100% isopropyl alcohol strip off the rear coating on a Tokina teleconverter once. Never again will I let alcohol near my optics except as a very last resort (hasn't happened yet) and only 50% or less.
Organic solvents can also damage the resins (plastics) used for the body, rings etc. of the lens. I've also seen 100% alcohol damage the surface of plastics, dissolve lettering and rubber parts. Using alcohol for cleaning is just asking for trouble.
Besides, IPAs (India Paie Ales) are better for drinking than cleaning.