Blu-rays have a protective coating already. A soft lint free 100% cotton cloth and water should be used to wipe them clean, from the inside to outside. NO chemicals unless you have major scratches, at which point there are acrylic polishes that are fine enough to use, but you still risk damaging the disc further. Absolutely no alcohol based products.
Those "disc washer" things don't work, so don't bother with them.
I have probably a thousand discs (BD, CD, DVD). I have cleaned a few of them in the last 10 years due to accidental scratches, but other than that, they should not need cleaning if properly stored in their cases or something comparable and handled with care.