Remaining Questions: Making Inferi

It's said that Voldemort killed (or had killed) enough people to make an army of Inferi. Meanwhile, we know that Voldemort had placed several Inferi in the black lake, where he placed the locket horcrux.

However, we don't see any Inferius attacks first-hand other than in that cave. And we don't hear specifics of any new attacks on the general populace since Voldemort's first rise to power. The Ministry warns that since Voldemort had used Inferi in the past he might use them again, but apparently he didn't. Looks like he only made them before attacking the Potters, not afterwards, and that they all ended up in the black lake. Why is this?

Dumbledore gives us an interesting hint about it, but the details are missing. He told Harry that Grindelwald wanted to use the Resurrection Ring in order to raise an army of Inferi. Though Grindelwald never found the ring (it was still in the possession of the Gaunt family), Voldemort sure did -- he stole it the day he killed his father and paternal grandparents. He was still known as Tom Riddle then, still a student at Hogwarts, still a member of the Slug Club, but he knew how to make a Horcrux by then. He obviously didn't understand that the ring he used to make a Horcrux also happened to be a Hallow. Peverell ring = Resurrection Ring. If he had known just how special the ring was he might never have turned it into a Horcrux. Did Voldemort make Inferi without knowing how he did it? Had he figured out how to tap the ring's ability to make Inferi without understanding the ring?

Is there another way to make Inferi without the Resurrection Ring?