Every volleyball player has their own specific position that they always play in, at least when you get to the higher level of play like high school, college, or even maybe club teams.
You can't have a great spike if you don't have a great pass to begin with. So, everyone seems to depend on your libero since all they do is pass and they're supposed to be your best passers too. Therefore your libero needs a lot of volleyball training. Not only do they need just libero volleyball training, but they should know everyone else's position incase they need to go in for some reason. Some training they should do as a libero is just getting used to receiving different kinds of passes off the net.
So, the coach could maybe spike it over once, set it, or even just serve it over and have the libero get the pass up to the target. Not only do their passes need to go the target, but they to stay low and not come up when passing. Also, make sure you review the spike approach with them just incase they would have to go in or even setting or serving wouldn't hurt.
However, since libero volleyball training is basically passing, hitter's training is slightly different. Hitters should get some volleyball jump training so there spikes can be more direct down and this would help with blocking as well. And on that note volleyball blocking drills aren't done enough and it would really help your blockers out. Regardless of what training you choose, you'll be sure to be a great volleyball player.