Doesn't have to be brown paper. It is useful as you can see the wax being pulled into it. But ordinary kitchen roll works just as well. Just be very carefull you don't have the iron too hot especially if the carpet is manmade fibres. If it is coloured wax then you would really be better off with a solvent as the heat can set any colours. Citrus gell type products work well, work in with a blunt instrument then rinse, repeat until happy. Don't forget if they have tried themselves there may be damage to the pile already.