Well..you could clean your brand new o-rings before lubricating them, but then you'd also want to clean your hands and don O2 clean gloves in your clean room before touching and lubticating your newly cleaned o-rings.
"O2 Clean" is a relative term and since you are just reducing the potential fuel source inside your reg (and will contaminate it to some degree the first time you use it, even with O2 compatible air, nitrox, or what ever) and given that you are not launching space probes to other planets, cleaning your new viton o-rings is a bit too much.
Just lubricate them with Christlube and install them in your O2 cleaned reg..