homemade dental treats?

I have two Chihuahuas; the larger, older one eats any treat she can get her mouth on, so she has no problem with Greenies or any other dental chewy, but the other one has a small head and mouth and refuses to put out the work that even the smallest Greenies (I just use this as a generic term) require. I've tried even the more expensive "heathier" brands, but he won't give more than a couple of chews and drop them on the floor, whence his "sister" scavenges them up and devours them. I was thinking of trying to make something just a little bit softer so he will eat them, but still hard and tough enough to clean his teeth. Any ideas for homemade dental chew recipes out there? BTW, his flatulence is pretty stinky, so I intend to add chlorophyll drops, seaweed/kelp or lots of parsley to any recipe to help out there too.