I bought the Paula Dorf Eye Transformer Brush upon the recommendations of several readers.Paula Dorf's Transformer is a sealing/activating solution that makes any powdered eye shadow or eyeliner cake into a waterproof liquid liner. I've been using it for years-- since those long ago days when the Paula Dorf line was available at Sephora (as were Sue Devitt, Alison Raffaele, Anna Sui nail polish, Becca... hard to belive now).
In any case, the Eye Transformer brush was designed to go with the product, and my friends mentioned it's also a great tightlining brush. And it is. The curved firm synthetic bristles get right where you need them between and just below the lashes and deposit any liquid, cream or gel eyeliner evenly. It's easy to use both this way and as a traditional eyeliner brush. The curved shape adjusts to the lash line and makes it very easy to do a very precise job with no jagged lines protruding and messing up your thin and perfect application.
Paula Dorf Eye Transformer Brush is a good alternative if you prefer not to use natural hair. Personally, I still find Hakuhodo weasel brushes (Kokutan E0189 and K005) to be more delicate and pleasant to use, but as a hardcore eyeliner user I go through several brushes every week, so this excellent Paula Dorf tool was a welcome addition to my collection.
Paula Dorf Eye Transformer Brush ($24) is available at the counter in Henri Bendel NYC and pauladorf.com.