Hypertufa, like concrete needs to cure for 1-2 weeks. It should be kept damp or moist to become strong. Otherwise it may crack - if it drys too fast.

I have ocassionally placed the entire project in a water bath ( to cure) after I taken it out of the mold. If you do that you will get a milky residue in the water from the cement. Washing with water will remove much of the cement residue.
I would not rush the project. Make one now and allow it to properly cure. Allow it to remain outside and ocassioanly hose it down to get rid of any residue from the cement. That and Mother Nature will help get it ready for the birds. There are hundreds of birdbaths made from cement and for sale at any garden center. I am not aware of anything special that is done to them.

Some may suggest to seal - I am not sure of the harm that the sealer may have. I have done both - sealed and unsealed. Mike

Hi
I disposed of my stone BB because they get so dirty so quickly and the only way I've found to clean them is daily brushing along with occasional bleach Have replaced with
plastic drip trays Very light easy to wash can even take them in the house to clean. only problem is they look like plastic drip trays l Working on that!! lol gary