What should I use to apply eye shadow, a brush or a sponge applicator?

It's really your preference. Eye shadows that contain a lot of pigment are best applied with a professional eye shadow brush, which blends strong color well. Eye shadows with less pigment may be applied with a disposable sponge-tip eye shadow applicator, which applies more product. To test whether your eye shadow has a lot of pigment, touch it lightly with a clean finger tip. If your finger tip shows a lot of color that won't rub off easily, the product contains a lot of pigment.