Like bobbythehunter, I use some dish washing detergent in water.
I've tried water, "Moose Milk", other home mixes and some commercial products, but did not get any better results than dish soap and water.
Note that milking a moose can be rather risky.
(Because the question frequently comes up:
One of many ways to make Moose Milk:
#1 4 ounces NAPA Auto Parts #765-1526 Soluble Cutting & Grinding Oil
1 ounce Murphy's Oil Soap
7 ounces 91% Isopropyl alcohol
16 ounces tap water
Another Way
Castor Oil 4 oz.
Murphy's Oil Soap 1 oz.
Witch Hazel 4 oz.
Isopropyl Alcohol (91%) 8 oz.
Water (non-chlorinated) 16 oz. )
I still just use water and dish soap.
Ron