You're experiencing what's known as a bad mix. Either the grout wasn't mixed properly (out of the can), or if you mixed it yourself, it wasn't mixed properly.
Unfortunately, you need to dig out the grout at least 1/8" for new grout to work. I know of no 'smoothing tool' to use. If you're read the directions on how to grout, do re-read them. If you don't have them, get them. ANd it you have 'cheap' tools or not the 'right' tools, get them. Certainly, you'll save some $$$ by having a pro do it. But if you're doing it yourself, spend some of that saved $$$ on good material and tools. THAT'S one of the reasons a pro seems to charge so much. Not only is his/her experience valuable but they use the right tools.
Other than that, you can search the WEB for sites on how to install ceramic tile. There are TONS of them with useful info. My best to ya and hope this helps.