I use a flat buki made by Honeybee Gardens. It's dense and never has shed. I use it to apply powder foundation. Another one I use is from Smashbox. It's the one that came with the shadow liner and it is an excellent brush to use for applying my Age Rewind Concealer.
Smashbox brush is bullet-shaped, not flat
Honeybee Gardens Buki, squatty little fella