I have used Propspeed on Elyse and on my previous boat with great success.
The only time it didn't work well was when I left the boat in the water for 4 months in Fiji and the prop grew oysters!
It seems to me it certainly works better if the boat is moving.
We haul out this month for antifoul, C-drive, bow thruster etc and will use Propspeed again.
Someone mentioned grease.....many years ago, BP - Before Propspeed, we used to clean the prop, sand it until it shone, heat it up with a heat gun and then paint lanolin grease onto it. That seemed to work OK, would last a few months, nothing like as good as Propspeed.