First:
http://screameleons.com/how-to-handle-your-chameleon-properly/
It freaks me out when people say they pick a cham up from behind... It inflicts TOO MUCH undue stress on your cham, which WILL shorten it's lifespan. Please, stop this immediately. Handling is not necessary, and a lot of chams don't like it. If he won't go on your hand, use a stick or a bungee cord in the same manner as shown in the videos in the above link to transport if you need to clean, otherwise handling is NOT necessary!
Second: A cup is literally a cup or a tall bowl - not a bottle. The aim is a container that your cham cam sniper shot from several angles and get food. He will want to be above the food, as is their natural hunting instinct, so place it lower than his favorite branch. If you buy crickets in the bins, just keep one of those after it is empty and use that. It just needs to be a few inches tall of plastic, glass or metal to avoid most things escaping. You'll get a few escaping crickets regardless, if you are feeding crickets. Accept this and know that this is what a good enclosure is for. Your cham will find the escaped ones!
If you want something nicer looking, there are some awesome DIY Feeder Cup tutorials:
https://www.chameleonforums.com/my-diy-feeder-cup-138734/
https://www.chameleonforums.com/diy-cricket-cup-135803/
Hope that helps. Cheers!