It won't make a significant difference if you clean the pad for the second panel with ONR. The Hyper Polish can be sprayed onto a dry pad and will work well. I think the advantage of using a pad which has been cleaned with ONR is firstly, you are starting with a very clean pad which is always a good idea. Secondly, my guess is the ONR is helping to spread the polish over the pad and maybe helps with lubrication.
I have used Hyper Polish with dry and ONR dampened pads, the difference is not night and day, using ONR makes it slightly nicer to work with.
One thing I have tried is to wash the pad in a bucket of ONR and then spin the pad on the polisher at the top of the bucket. Care is needed here as water and electricity can create some very unpleasant outcomes. The ONR bucket method is probably not as good as a fancy pad washer but is much cheaper.