Ali Al-Chalabi is correct, brake fluid is very corrosive. You should not get on any painted or other steel surface with air around, but once you do if you rinse it off with lots of water you will neutralize its corrosive tendencies. The water essentially uses up the brake fluid's corrosive potential very quickly and thoroughly. So raise the hood and hose the area down. Take care not to splash the stuff if there are puddles of it so it gets on the exterior as it may stain or damage the paint too.
I would also not worry about overfilling slightly as long as you do have some free space above the fluid level before you get to the top of the reservoir. Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)