You don't necessarily need to study for hours in your spare time to do this. Usually when people talk about studying to pass a Big 4 interview they're talking about brushing up on the algorithm stuff and not learning some new tech. For the sort of thing you're talking about, finding your way into jobs working on cool stuff will often provide the boost that you need.

IMO all but the most serious of side projects tend to not build enough experience to pass an interview for Technology XYZ anyways so unless a company is willing to deal with a newbie, and many are, it doesn't matter that much.