1) Mayim Achronim does not require a utensil, nor does it require "Koach Gavra, force of a human" like the washing of Netilas Yadayim.
The source is from the Mishna Berurah, 181:21
As far as whether to wash into a keili or not, the same site says this:
Rather, the water should be washed into a utensil that is designated as a receptacle for the water, which should then be disposed of. (See Biur Halacha Siman 181:2)
However, if the water is being washed onto the floor that is under the table, where nobody will walk, it is permitted to do so. Still, if a utensil is available in which to wash, that is better than doing on the floor under the table (Mishna Berura Siman 181:4-6. See also Shulchan Aruch HaRav Siman 180:4)
2) Mayim Achronim may be washed directly into the sink, as people who are stringent to use a Revi'is as the Gaon of Vilna held, do in any case. Some maintain that the water must be washed into a utensil, and not in the sink, however the prevalent minhag is not to require this. (See Shu"t Yabia Omer Vol. 5 Siman 2 and Likutei MaHarich end of HanHogas Seudah quoting the Shl"a HaKadosh.)