Required techniques vary from area to area and problem to problem, that said I think there are 3 techniques that are universal. This belief stems from my philosophy that the best thing about climbing hard is that there are more cool problems that you can climb. This is not to say there are not cool V2s (or even VBs, but a V5 climber has access to everything that a V4 climber has access to and more. My second belief is that climbers only break out the technique when they lack the power to climb it properly.
The first is topping out. Unless you are really lucky, indoor bouldering does not generally require/enable/allow you to top out. You get to the last hold and drop down onto a bunch of cushy pads. Outdoors, you get to the last hold and now you got to figure out how to get over the lip. In generally, involves a mantle of some sort and your feet really high. You blow the top out and it is likely you are coming off head over heels.
The second is power. At the V2/V3 grade, there are not many problems that stronger climbers cannot do while wearing approach shoes without jamming, heel hooking or any other technique like trickery. Enough power will get you through almost any V3 (and a lot more). Sure, really good technique applied to the appropriate problem will get you to the top, but if you can only choose one tool for your arsenal, power is not a bad one to choose.
The third is enough open hand strength to allow you to deliver your power to the rock. Sure some holds are better crimped and others should be jammed, but again, if you can slap a hold and have your hand stick to it, that should get you through most V3s.
As for route finding/reading, at the V2 level, in all but the most isolated areas you will have plenty of access to beta. Even in the absence of beta (and chalk), if you have enough power, it doesn't matter if you miss a key foot hold or your hands are backwards.
As for differences in indoor and outdoor grading, this often depends on the area. Indoor bouldering at the V2/V3 level is often on steep terrain with either big jugs far apart or moderate holds close together. Outdoor V2/V3 is often less or near vertical. This means that power that you develop in the gym is less useful outside, but as your indoor power grows and you start to climb steeper problems outside, that gap will close.