mix the plaster of paris with anything tiny and dry like sugar and flour, rice , the recipe says equall parts ie 1 cup of each, anything dry as i assume as soon as it get wet it sets (when the rat drinks)... will try a mix in a saucer then add a drop of water . (thers no nice way to go for a rat) ive sat there for ages with a gun and got 1 or 2.... what did work was i got a cd of ebay of vermin calls foxes rabbits elk all sorts... one was of rats feeding, i got a personel cd player and mini speaker and it did work , they came out within minutes, one day i forgot it and they didnt come out till dark. you can download it on your i phone...... shooting takes forever