Eastsidepilot's work bench
Mick,
MDF is very easy to work, it's a bit dusty but please all ways wear a mask, the damn stuff contains formaldehyde and you don't want that in your system.
It is quite fiberous and tools need to be razor sharp for best results, it also sands very easily.
In this case I have used ordinary hand tools, in the case of the backs, these are made using just a rebate plane and a marking gauge, then sanded.
I clamped a piece of 4mm mdf to the bench, then set the gauge to the depth of the seat back, this is run down the edge of the board a couple of times to put a deep gauge line into the mdf, then I reset the gauge to the depth of the top section of the seat back and regauge again, quite deeply.
Then take the rebate plane, minus it's fence, and place it at an angle to the surface of the board so that the bottom corner of the plane is resting in the gauge line and take a fine shaving off the full length of the board. Turn round and take another pass on the opposite side of the gauge line and you will have a perfectly straight, very shallow 'V' you can then sand the profile of the seat with fine sandpaper. once finished the strip is cut off with a hand saw and the process started all over again, till you have enough material.
Hope that all makes sense,

if not tell me and I'll post some diagrams
Col.