I had actually considered mixing sand and glue and then painting the inside, I think it was TeleVue that did this at one point? They’ve also used a flocking felt as well. I have an older Zeiss 135mm F/2 that has felt on the inside of the light shield.
Looks like ScopeStuff is the way to go, it’ll certainly be easier to deal with than the Bunnings stuff as it’s quick thick and as you mention Alex, no way of knowing if it’ll leave a mess in the long term. It does look quite a lot blacker when seen front on but it gets shinier with incident light which is what is seen more so in astro applications.
It was a worthwhile $6 test though
