Pattern types:

DEW is the most basic expression of the gene - usually expressed with the nDw (heterozygous) genotype. The dew marking is a vague lightening of the topline, like a reversed dorsal stripe, however much wider and wispier.
Dewing only extends about 2 hands beneath the topline at most.

DEWFROST is essentially a heavier version of the Dew colouring. Dewfrost can extend much further down on a horse, and the lightening of the coat is usually far more extensive - often spreading down the slope of the shoulders too. The Dewfrost pattern can reach anywhere from just off the topline, to halfway down the legs, depending on the bloodlines.
Dewfrost can appear in both the heterozygous nDw and the homozygous DwDw.

DEWCANO is an interesting phenomenon that can be found with the dew gene. Essentially, this pattern is a flipped rabicano that stretches down from the topline to form streaks of white across the barrel. Dewcano always starts just behind the shoulder, and from there it can extend to cover most of the back.
Like Dewfrost, Dewcano is found in both nDw and DwDw horses - the strength of the gene will determine just how extensive the patterning is.