I am no expert and I expect those more experienced to chime in, but I fed dry sugar and here are the mistakes I made:
1. Didn't get it wet enough and some fell through, getting trapped between bottom screen and bottom board. When I cleaned it out--by shaking it into the weeds--I attracted tons of bees, solitary wasps, yellow jackets, etc. This frenzy set off robbing.
2. I put syrup above the inner cover when I first started and got ants. So now I put everything inside the hive, on the frames (inside an empty super). I do not know how I'll handle this in the Winter when I don't have an empty super. I might try the sugar candy for winter, and replace one frame with it. Looking for suggestions on this.
3. For feeding dry sugar, I put heavy paper down then the sugar on top. (I now put the sugar in an empty coffee jar, add water, and shake. This way I can make sure it's wet and it's easy to transport). The bees eat through the paper and leave holes in it. It's hard to move the sugar if you want to inspect. But it's easier to feed this way. They seem to go through 4 pounds pretty fast, though. I don't know why people don't just put it in a bowl?