Painting bathroom tiles - tips or very cheap alternatives?

I've just painted over tiles at college for my P&D course, we cleaned and sanded the tiles down so that the paint has something to grab on to (keying) we then used a white oil based undercoat (resistant to water) then re keyed with fine wet and dry and painted over with oil based colour of choice. You could then get a grouting pen and go over where the grout lines should be if you want it to look like tiles again. Have fun!