I still feed crickets but I buy in bulk and and house them away from my chameleons. I don't buy crickets from pet stores or other places that house chameleons. I keep any dry gut load in a tray that doesn't get any damp gut load near it. I keep things ventilated so condensation doesn't build up.
I use a
feeder that keeps crickets in and I have a pretty good idea how many to feed per day. The occasional cricket could get into the cage but rarely. Other feeders not at all. The feeder is covered on the top so chameleons tend not to poop in it. It's very easy to clean.
If you don't want to do that you can just keep any uneaten crickets in a deli cup and gut load for the next day. They just need to go back to same cage they came from.