Download the image [full size]. Make sure that it is 250 by 250 Bmp.
Open the file in Medibang. [ Not sure about how FireAlpaca is set up]
Go to add brush bitmap, third on the bottom. Go to file from canvas.
Copy the settings on the side if you like the outcome.
If not mess with the settings yourself.
fur brushes are weird and some only seem effective when you go in a clockwise motion.... basically left to right.... If I don't have at least 10 brushes up here that means that I'll be updating the journal