Yes, you are effectively using it as a solvent to remove old oil / grease that might be causing the diaphragm to stick. So you need to strip the shutter out of the lens first. However, trichloroethylene (trich - ask Tom he might be able to get you some from the engineering shop, or ask an electronic engineer as it's used as a de-greaser prior to soldering sometimes) would be better. Once it is de-greased / cleaned you can then use a tiny amount of watch or sewing machine oil on the mechanism and re-assemble. Don't get any solvent on the lens elements though as you might damage the adhesive used between elements etc (and any coatings if there are any).