1) One usually only feeds from the bottom if the slurry tends to settle. Otherwise, we feed from the top corner. We rarely use center feeding.
2) One should wash from the top left cross-wise and out the bottom right.
3) Always blow down from the top to the bottom so liquid drains out.
4) Countercurrent, because one wants the wash to go through the cake (i.e., from the top left to the bottom right or from the top right to the bottom left depending      on how the press is ported).
5) We never dilute the feed since thicker slurries are generally easier to filter.
6) Altering feed solids isn't a good idea based on (5) above. Variable feed rates are generally accomplished anyway as the cake builds up. Hence, one starts at a fairly high flowrate to fill the press, which then drops off fairly rapidly as the cake builds up. This is why pump selection is critical.