I know several folks with awarded Phals and every one of them uses the whole milk approach as part of their pre-judging prep routine just as Ray mentioned earlier.
I've never cared if my Phals' leaves were shiny or not, but I like them clean. I have a mixture of species and hybrids, and some naturally have shinier leaves while others have more of a matte appearance. Leaf color, texture, size, and shape also differs greatly among them. They each have their own unique characteristics. I've never used any product to make them shine, but I do periodically moisten a paper towel with plain warm water and gently wipe each leaf. I use a new paper towel for each plant.
If dust is the issue, you can spray them at the sink, or in the shower. During warm weather mine dry so fast I don't need to worry about rot so I don't bother drying the crown. If I did this in winter I would blow the water out of the crown.
__________________ May the bridges I've burned light my way.
Pre-covid I entered an Echeveria in our county fair. The leaves had a lot of spots from hard water, so I cleaned each leaf with a q-tip dipped in mayonnaise. It worked great, left the leaves clean and shiny and didn't seem to harm the plant. I only did this once, and rinsed it well when I was done. Won a well-deserved second place ribbon
I've never tried it on a Phal, I just rinse off the leaves at the sink and don't worry about shiny.