Most waterproofs have the mix ratios on the back of the tub , normally its linked with the amount of cement you use per mix , say for example 250ml per 25 kg of cement , so if its a small belle type mixer and your using half a bag of cement per mix add about 125ml of waterproofer , keep the amounts the same for each mix by using a measuring jug or find an old plastic drink bottle and cut in down the amount you need . As for the top coat you can just use feb or feb and lime just don't over plasticize .