Playing around with the new Humbrol Weathering Powders at the moment.
There are around 8 different powders available from Humbrol. At present, my local hobby shop only has 3, Black, Rust and Dark Earth - so its these 3 that I've reviewed.
I chose an Airfix WWI Female Tank for the weathering process.
Overall, the powders are ok, they do go on as indicated by the Humbrol YouTube, and can be worked with the Humbrol range of Enamel Thinners, MattCote and DecalFix.
The powders look like someone has ground up a chalk pastel stick of colours. You get varying sizes of dust particles in each bottle. They can be worked onto the model with paint brushes. Humbrol MattCote and Thinner can be used to apple the powder and hold them in place. DecalFix and water can be used as well, although the MattCote is the better alternative, as its a bit more resilient to handling. I find you can work with both mediums for awhile, however after a few hours the MattCote/Thinner mixture is difficult to work with. The other medium is still workable after a few hours.
The powders are messy to work with, so make sure you are prepared for a messy work area and hands.
I'll post some videos below of my earlier attempts at using them. Although I hadn't tested decalfix method at the time of the videos being created, I have tested them since. They do work well in this medium.
My tip to everyone, use very cheap or old paint brushes, as applying the powders can damage the bristles, especially if you want to create a caked on mud look.
I have mixed the powders with Tamiya weathering powders and get similar results.
In the videos, I'm also reviewing the Airfix Female Tank and creating a diorama.
Here are the videos;