In fact, there are few things to know about selecting vertices/faces efficiently with Misfit :
1/ use one wireframe view as an orthographic view (you can Ctrl+click + drag your mouse on a view to move around your object, and Ctrl+mousewheel over a view to rotate it)
2/ select roughtly your vertices/faces/whatever
3/ deselect things you don't want to manipulate
4/ if you can't deselect extra stuff at once, move around (1/) and deselect (3/), and do it until you have only what you want.
Remember: always select roughly THEN deselect. (For example, it is impossible de select a face without selecting some backface, that why the deselecting phase come after).
BTW, you can use "grouping" extensively, then you can easily "hide" part of the geometry. So even when you have a lot of vertices, hiding 75% of them allow you to model particular things without loosing time and nerves.
I can ensure you, that using Misfit is really far more easier than using GTKRadiant for example.
(Of course, Misfit is designed for creating map object not a whole scene, but working on object with GTKRadiant is definitively bad).