Personally speaking i prefer a foundation that is highly concentrated - i.e. - one that is full coverage. That way i can control the product and the intensity. I would rather sheer down a full coverage foundation than have to apply more product (thus using it up quicker).
The following foundations are among my favourite liquid foundations.
If you're looking for EXTREME cover (i.e. - scars, tattoos, birthmarks etc...) then illamasqua rich foundation is best of the best for that.
Bobbi Brown SPF 15 Tinted Moisturizer
Clinique Almost Powder Makeup SPF 15
L'Oreal True Match Super Blendable Makeup SPF 17 Sunscreen
Laura Mercier lluminating Tinted Moisturizer SPF 20
Ellis Faas Skin Veil Foundation
NARS - Sheer Glow Foundation
NARS - Sheer Matte Foundation
Regardless of all the best foundations brushes available i still prefer to use a damp sponge. This stops the foundation from being overly absorbed and it also allows for the most beautiful application. The beauty blender is still one of the best tools for foundation. A wedge sponge is just as good...and cheaper.
Always use less product than you think you need - you can always add more.
I always (almost always) set foundation with a powder and a puff. This seals the foundation in all day ensuring it will require very few, if any, touch ups.