You don't really need the Dia-Flat. It will work but is a bit of overkill. That is for lapping (flattening) hones but it is quite aggressive and for that reason is not ideal for refreshing the hones' surfaces. You will be refreshing the hones a lot more often than than lapping them. In fact, regular refreshing has the cumulative effect of keeping the hone flat.
You would be better off with a higher grit plate.