You could always make your injection thicker by using less water (or whatever you use) when mixing it up, right? Wait, that's too simple - am I being punked?
, fresh papaya and pineapple both have enzymes (Papain and Bromelain) that break down meats and 'tenderize'. Packaged pre-marinated flats will often be treated with these enzymes. Nobody on this forum need mess with the stuff though.