get some proper different grades of paper... not sure on the grades you should use, I think youl need 400 and 600, but you better ask. Start off with the roughest to get all the texture off the parts you want to spray, then use the finer stuff to get it reaaaaaally smooth.
Then clean everything with white spirit, just wipe it over with a cloth.
Then spray everything with a plastic primer, just in light coats, let it dry between coats - maybe give it 5 coats all together.
Then sand down lightly with your fine grade paper to get it really smooth again.
Then get the colour on, let paint get tacky between coats, maybe give it 5 coats of colour aswell, thats what I did anyway! Very light sprays each time so it doesnt run, take your finger off the button at the end of each left to right movement. (dont turn the corners with it spraying basically)
Then while its still tacky, spray it with clear lacquer, again all these things are available in aerosol, just go to halfords if you have to, but maybe your more intelligent local modifiying shop can supply it all. Give it as many coats of lacquer if you want, again just build it up, wee coats at a time, 10 mins in between coats.
Make sure you do all this in a totally dust free area, and make sure there is loads of ventilation, otherwise your gonna get high.