Instead of filtering the fine black sediment from the zinc precipitation, simply alllow the solution to settle and siphon off the liquid from the fine powders. Test the solutoin for PGMs before proper disposal.
Wash the fine powders into a smaller beaker with a spray bottle.
Add a dilute 10% solutoin of HCl (muriatic acid) and allow to react until all fizzing (tiny streams of bubbles) is completed. This removes any zinc left over in the powder.
Allow to settle again and siphon. Now process the mixed PGM powder with a minimal amount of AR as shown on the DVD.
If you used fine zinc powder as shown on the DVD you will likely encounter an insoluble sand like brown powder. This is Cab-O-Sil (SiO2) a stabilizer added to powdered zinc for shipping purposes. I found this out after making the DVD.
Steve