Dust sheets are useless Steve. Use the heavier drop sheets available from Prochem and others or, even better still is the old cotton sailcloth, but this is rarer than hens teeth. Absolutely essential if the floor is polished is to use a polyprop or polythene sheet under your drop sheet. Mr. Safecleanlakes advice about areas that could be oversprayed is essential too, and make sure you stand your machine, buckets, tools, sprayers etc. on a waterproof mat too. Otherwise you may have re-polish job on your hands.