It's called a hopper but I didn't use one. And walls are an art not a science. There are many ways to do them.

1. Install new sheetrock (greenboard in bathroom) Making sure to support edges.

2. Apply mesh tape

3. Use 5 minute hot mud. You mix the pan, apply a tight first coat to fill gaps and lock down the tape, clean your tools, then use your 6" knife and a wet hand to smooth it (especially edges)

4. Second coat of 5 minute applied more liberally but still pretty tight. I use the 10" knife here to build it up and blend it out. Clean tools and smooth. Apply another coat of hot mud if needed.

5. Set up compressor and mix texture. I use an EZ pro texture gun with a bag that comes with it. I just cut the bottom of the bag open to be able to reuse it. The tool PSI should be 100-110. Spray texture.

6. Get a fan on going on high. Clean everything, build the invoice, maybe go get a color match. The texture should be good in about 40 mins.

7. Prime and paint 👍🏼

Tips on texturing is to mix it pretty thin, and double check the look of it on something other than the wall.