You'll need at least 1/4" of hair growth for it to be removed. Apply the sugaring gel in the SAME direction of hair growth with applicator at about a 45 degree angle at a section of hair smaller than the strip you're using. You want the product to coat the hair, but you don't need a ton. If you apply too much, you'll have a problem removing the hair or break it above or below the surface.
Large applicators (buy direct) are great for the body and smaller ones work better for more precision on the face (buy direct). Most of the wooden applicators have rounded edges, but square edge applicators help make getting the bikini line straighter (buy direct).
Sugaring gel has also been called sugar wax, because it's applied similar to waxing- but it's not a correct term. Sugaring paste, on the other hand uses a different technique that takes hair as short as 1/16 of an inch and doesn't require strips or applicators.