The Plasti-Kote spray paint (B&Q, £8 a tin) along with proper MDF sealer does a fantastic job (don't prime with diluted PVA as not recommend, seals surface too well and prevents paint penetrating and doesn't sand properly).
Plasti-kote, Welcome to the home of spray paint
Need to set yourself up a protected area to spray. Outside might be OK, but wind, passing insects, dust, cold etc all work against you. I sprayed my MDF sheets in the garage, making a "spray booth" out of dust sheets hung from the ceiling (to protect everything else in the garage..). Also lit with 500W lights so I could see what I was doing, heated with fan heater and hung all the MDF pieces from the ceiling so easy to work with.
Remember to turn off fan heater before spraying as a fire risk. Eye protection and face mask are essential or you will be coughing up stuff the same colour as your sprayed for next couple of days.
Just spray numerous thin coats 5-10minutes apart (or what ever can says). If you leave to dry too long next coat either won't stick or will eat into the layer below....
Leave 24 hours before adding protective spray varnish coat.
You will need far too many cans than you initially guessed at. I am sure it said 1 can does 1 coat for 2 square meters. I used about 6 cans for a baby changing unit/cupboard (same size'ish as 90cm tank unit) and 2 cans of sealing varnish.
Unit looked the doogies danglers and was easy to wipe clean etc. The other unit I worked on I rollered (as described above) as spraying was far too expensive and time consuming.