Wet and mushy is good. That means the microbes are having a feast. Since worms don't have teeth, and it is the microbes that they live off of, wet and mushy is what the worms need.

When to add more food is something that you will have to learn to judge for yourself. It may take a few days for food added now to become wet and mushy. I would wait until the food in the bin now is mostly gone, but not completely gone. That way the worms will be finishing off the old food while the new food begins breaking down.

Part of this will depend on how much you feed, what you feed and how you prepare it. Some foods take longer to break down or have a strong odor no matter how well you manage the bin. Other foods break down quickly and don't smell.

Yes, wait until the food is all gone before feeding again. Mushy is just fine. They will eat it all. Sometimes when starting a new bin, it takes them a while to adjust.

I wrote a page on feeding worms if you want some more info.

Good luck and don't worry too much. ;-)

Here is a link that might be useful: Feeding Compost Worms