I go through several concealer brushes a week. Using them with liquid and cream products renders these brushes sticky and cakey after a single application, especially the thin and flat ones. While I prefer thicker concealer brushes that can also blend and buff the product for a natural look, the flat type also has its use especially when one only needs a light patting of concealer to even out a small area.
Sephora has always offered concealer brushes in several shapes and sizes. One of my oldest surviving concealer brushes is a thin and pointy brush from their original brush line that didn't have names or numbers. The two brushes you see here #46 from the classic black handle line and #45 Platinum Pro are hard working and good for what they are even in comparison to more prestigious brands.
I go through ups and downs with the #46, mostly because I'm not loyal to one concealer and I've found this brush's performance depends on the product in question. The #46 is made of firm synthetic talkon bristles that work best for patting down medium-thick cream products. This brush is useless at blending and buffing and was not meant for tasks that require flexibility, but if all you need is to lay down products (including primers) this is as good a brush as any.
Sephora #45 Platinum is a different story. The talkon bristles here are soft, densely packed and perform well with different textures, including thin liquids or sticky pastes. I find this brush to be better at blending than Smashbox #5 and far superior to Chanel #1 (not pictured and probably the most useless concealer brush I own as it cakes at first contact with the product even before it actually touches my skin).
Bottom Line: staples.
Sephora Concealer Brushes: #45 Platinum ($21) and #46 Classic ($17) are available online and in store.