There are a number of websites that sell trapping equipment. On ething I've been meaning to buy because it's so very useful is a trap/cage comb. You can use this to squish a cat to the side of a cage to give him shots (thereby allowing keeping a feral in a cage prior to veterinary work) and you can use it to separate two cats caught in the same trap. I know this can be done anyway by sticking pieces of metal through the slats to make two separate chambers, but I don't have such pieces of metal either and think the trap/cage comb would be awfully handy. The Alley Cat Allies liaison in my state puts one to great use.
Something else I find invaluable in working with ferals is 2-door cat cages, small enough to fit in my car. The 2 doors allow potentially changing kitty litter etc if the cat is not a spitter. For spitters, if I cage them (which I usually do not), I feed them on a paper plate which I fold in half and slide through the rungs and let it unfold on the other side. Water added to the bowl like watering a plant. If the cage needs cleaning, I mate the door with another cage and poke the cat into the clean cage.
However, I usually keep cats in traps until they hav ebeen to the vet as it is MUCH safer. There is NOTHING worse than losing a cat. It is easy to mate two traps and poke the cat through to a clean trap without any chance whatsoever of losing him. A lost cat may die far from where s/he knows to go for food and shelter. Putting out food will not help because s/he will be long gone.