Since Oversoul is mostly used in a Elemental HERO only deck, one of the better ways to send a normal Elemental HERO is through Blazeman's effect. Use Blazeman to send Elemental HERO Neos from your deck to the grave. This will make Blazeman's attack and defense the same as Neos. You can then use Oversoul to special summon from your graveyard. Alternatively, you can use Blazeman's effect to send Elemental HERO Necroshade from your deck to the grave, so that you can normal summon a Neos later if you get him to your hand.
Special summoning them is useful to fusion summon another monster. If you already have the other monster material on the field, or by using fusion substitute like King of the Swamp, you can attack up to 3 times.