Need help with Lumby Easy Diary - with a twist

I have a level 3 skiller, and was hoping to complete the Lumbridge Easy Diary. I need to kill a swamp rat to do so, but it proving difficult. I attacked the rat with a rubber chicken, then stood there with a ring of recoil and an inventory of lobsters. But I run out of food before the 10 damage from the recoil can kill the rat. Am I missing something? Are recoils useless now? Is there a better way to do this?