Start with a clean press, add up to 2 cups max and with the syrup at 190 or more, run that thru the press and back into the mixing tank. When the syrup coming from the filter looks sparkly clear, stop the press and move the hose to your bottler or a barrel. Then for each additional 5-6 gal of syrup in that same session add up to 1 cup DE, mix it in and send it thru the filter. With each new batch of 5-6 gal, add 1 more cup of DE
You were filling the hollow plates with your initial charge, that is why it plugged.
Late in the season you might need to add an additional 1/4-1/2 cup of DE per 5-6 gal batch.