I just did some in Scarlett Red and Navy Blue. I used the powder die which worked perfect. Came out exactly as I expected. I just used 1 full pack of powder die. I didn't have any issue with it being messy, just be careful when opening it.
I used a large stainless pot filled with enough water to cover the props when added by about 2 inches.
Basically, take the water to between 90 and 95 degrees Celsius. Add die and stir for a few minutes until it is all disolved.
Add the props and set your timer for 20 minutes. Stir the water occasionally (say every 5 minutes) and after 20 minutes they should be good to go. I actually was curious so I stirred a bit more, but I don't think it had any bearing on the result. I also actually took the temp up to 93-94C and then shut off the heat and when it got to 90C degrees, I would turn the heat back on for a minute or so to get it back up to 92-93C and then turned it back off. I only had to turn the heat on once during the whole cycle.
I then moved the blades to a another container with some clean water as a pre-rinse and then just washed them off under the sink.
I will say, if you look at them as you are doing it, it doesn't seem like they are taking the dye as much as you would expect, but I can assure you, after the 20 minutes, they will come out completely dyed.