Simplified,get a tube of g3 or halfords equivalent,you maybe ok for a one off with the machine your neighbour gave you,but generally the anglegrinder type is the boy.

Be careful,as it can easily burn through the paint,so keep the head moist.start the machine up on the slowest setting(if it has one) and slowly pass it over a relatively inconspicuous area,say the door bottoms to get a but of practice in.you should see the difference immediately.

When your confident enough,carry on with the car but pay particular attenion to edges,badly faded areas etc as that will be where you burn through the easiest.

It makes a proper fucking mess,but your car will look the bollocks afterwards.

When you've "compounded" it all in,i.e. the harder head,then get a load of water over the car and run the polishing head over it,you could just give it a thorough clean if you prefer.

After all that,a good thick coating of autoglym in your usual way and it's going to look stunning.