I use methanol. Enough drops on the lens to cover the surface, lay lens paper on top, wait for paper to soak up methanol, slowly drag until end of paper or methanol is gone from lens. Do not reuse paper if more that one pass is needed or doing multiple optics. Do not press paper onto lens or drag with any pressure on the paper on the lens.
Other chemicals tend to leave a residue on the lens that can either damage the coating when the laser is fired or attenuate the beam.