I love this concealer, it's my new go-to. I've got very pale, sensitive skin with blue undertones, and the shade 00 Fair works well for me. It is a bit warmer of a color than I'd usually go for, which at first concerned me but ultimately isn't an issue at all. I think it actually ends up helping me with some color correcting, and a little goes a long way so I don't have to cake on too much. I usually apply and pat to blend with my fingertips, but those tiny beauty blenders might be a good product to use this with for more control. A full size beauty blender is too big and a brush doesn't blend this particular formula well, IMO
Coverage is definitely buildable, which is important to me in a concealer, and it doesn't dry up over the course of the day and get dry/cakey looking. The flip-side of that is that it's very shiny due to the oil base, but takes a finishing powder really well.