The real art is learning to judge ink consistency in relation to the condition of the matrix. Gene Laughter says he's seen a group of bromoilists take the same matrix (exposed, developed, and bleached identically) and each one soaked it for a different time or at different temperatures, and each one mixed his or her ink according to his/her own methods--and they all made viable bromoils. So there is no set way to do it--there is only the way that works for you.
I think it is important to see an experienced bromoilist ink a matrix at least once, and I'm looking forward to seeing how different bromoilists go about inking their matrices. I learned a lot just from watching Gene do his.
It is good to learn with a brush, but to start you simply have to get a lot of ink on the matrix and the fastest way to do that is with a roller. The white foam rollers sold at Lowe's are the best I've found. They are also good for clearing high values and rendering fine detail, even if you have done all the previous inking with a brush.
It is important to learn various methods for removing unwanted ink. The traditional method is "hopping" with a brush--either an uncharged brush or one charged with very hard ink. A wet paper towel can also be very useful, as can the cosmetic foam wedges that women use for putting on makeup (slightly moistened). Another means is to place the inked print in a tray of water and take a brush to the high values--sometimes this is the only way to clear delicate high values. You can use a knife blade, but that works best when the print is dry.