As far as I know, the Bain Online Test (at least for South America office) is separated in two parts: 1/ "gmat type" questions 2/ business case.
The first part includes the critical reasoning, the data sufficiency and the problem solving. There is no secret here. The more you prepare, the faster and the more confident you will be in the test day.
The business case is only mulitple choice questions. The most important thing is to be able to analyze and interpret charts. If you google it, you'll find material to prepare for it.
Hope it helps, if you want pm me,