I have had success feeding several orb weavers and such that didnt make a web yet. I would catch a moth about the same size (if anything smaller) of the spider and use my forceps (or tweezers) and get a solid grip on one of the moth's wings. It should now start to flutter with its other wing, whilst fluttering SLOWLY bring the moths fluttering wing in contact with the spider (usually next to the spiders longer front legs). When I say slowly I mean start at about an inch away from the spider so the spider's hairs can sense the fluttering and centimeter by centimeter bring the moth closer to the spider; the final distance should be most of the moths fluttering wing in contact with spider. When you see the spider start to 'attack' the moth wait til your spider has a good grip on it before releasing the moth. The same can also be used with a fly (like a blue bottle), except instead of holding it by the wing, hold it by the fly's abdomen (dont be afraid to get a good grip on the fly's abdomen it will eventually get eaten by the spider
)
Hope this helps,
Andrew