Recently, I was able to get a clean etch for the first time. I had the leave the wafer in 2.3% HF for 50 minutes in order for it to fully etch.
As for masking, I used duct tape. Originally, I used “car vinyl” because I though it would give me the best adhesive. But, I was getting lifting off the vinyl and I was etching in areas I did not want etched. Duct tape seemed to work well.