What is considered the "proper" way to increase the player's speed?

What I have now is a Magic Effect that modifies the player's SpeedMult. But triggering that effect through an item (the way this mod is supposed to eventually work) has no effect. Directly modifying the actor value through player.setav and player.modav (seemingly) do nothing. Modifying the actor value with player.forceav works, but only after I tap either my sprint or walk keys (i.e. not instantly).