It's definitely not the first thing one should do with their Mosin. Once the bolt and receiver have been thoroughly cleaned, the gun is fairly operational. A bit of sanding and polishing in key areas, plus lightening the spring, will make your Mosin a much more enjoyable weapon to fire. There's no one "this fixes the bolt" step for these things, it's a combination of many smaller things that adds up to a smooth bolt. Initially, most Mosins' issues with stick bolt stems from needing a good, thorough cleaning. That makes them useable, in my case, it took ALOT of cleaning of an otherwise clean rifle, to get it to last more than 10 rounds at the range (at which point my bolt would completely freeze, and I would literally have to stomp on the bolt to open it).
There's different grades of "bolt smoothness" that one can achieve, and trimming the spring is one of the later mods to do to achieve optimal operation speed.