Problems with my moms boyfriend?

Okay so my moms boyfriend moved in with us about a month ago. Im 14, so I still have to live with my mom... Anyways everything was fine until he started cooking dinner for us all the time, and he would always make the oven messy and he would never wash out the food in the dish before he put it in the sink. One of my jobs is to clean the kitchen every night and wash the dishes. I asked my whole family if they would please rinse out there dishes because it makes my job a whole lot easier and quicker. The dishes still always had food in them, so I specifically asked him to rinse out his dishes, so the drainer would catch it and he told me " I cant rinse them out and cook at the same time." Im getting so tired of wasteing 10 minutes just washing food out of dishes that he cant take 5 seconds to do himself. And also spending 5 minutes washing the oven and the counter. I mean I dont except them to be crystal clear when I wash them, because part of the job is to actually wash the dishes.. But he doesnt get that it would help a lot if he did it, and I have other stuff I have to do also so it takes up an hour of my night... My mom told me to just ask him if he would but I did, 3 times, and I even put up a sign, to remind him. Also, im not the only one fed up with his sloppy ways. Im tired of having to clean everthing, just to have him dirty it up the next day. So does anyone know how I can ask him to wash out his dishes and simply clean up after himself?