Their first aid kit is in ours, but the things we use most are gauze, microporous tape (12 and 25mm), antiseptic cream. Also use an emery file (for beaks), nail clippers (for claws), scalpel and have a very small sharp pair of scissors. We have coagulant powder for serious bleeds, like combs and wattles which sometimes just won't stop. Plastic skin spray for after the powder. Have a selection of syringes (no needles) for applied drinking. Cotton buds and cotton pads for cleaning them up after bleeds. A handy hair dryer for after bottom washing (they like it).
There are a lot of things that we don't use now. Probiotics, (because the rearers here has them included), stockholm tar (so messy unless left to evaporate and thicken), anti-peck spray (we fit a beak bit to the culprit), assorted Red Mite treatments (we steam clean coops). We have some Frontline spray just in case of a Northern Fowl Mite attack, but haven't used it for years fortunately. We also have lice powder but prefer a small squirt of cat flea spray and haven't needed that for years either.