lots of brown flakes in oil?
not a good sign, sounds like damage in the clutch packs, excessive wear. Did you find any metal particles too? they usually stick to the filter or if the drain plug has a magnet on it they are all stuck to it, you may find some floating around in the oil. Remove the filter and cut it open and see whats in it.

as for the pressures there are many to check
all pressures are checked at operating temperature (50C) at 2000 rpms.

Port1 (pump pressure) 965 to 1170kPa (140 to 170psi)
Port2 (Fwd Clutch Pressure) 724 to 860kPa (105 to 125psi)
Port3 (Rev Clutch Pressure) Same as forward (not more variance than 70kPa (10psi) between the two)
Port4 (torque converter) 724 to 827kPa (105 to 120psi)
Port5 (oil cooler pressure) 105 to 175kPa (15 to 25psi)

Test port locations:
Port1 is located behind the filter next to the dipstick on top of the transmission.
Port 2 is located in front of the control valve on top of the transmission in front of where solenoids are mounted.
Port 3 is located on top front right of transmission (2 identical plugs, one in front of the other) its the one behind
Port 4 is located back where the port 1 plug is but to the right of the oil filter almost center.
Port 5 is located up where port 3 is in front of port 3 in very corner.

You'll need an allen wrench (or allen socket) to get these plugs out and probably need some metric adapters to adapt your pressure guages. Go to a hydrauic hose and fitting supply shop and they will probably have them.