Toe separators, made of foam or silicone or even lamb's wool, are helpful to prevent friction when hammer toes rub up against each other when walking.  Although this may relieve the pain or friction causing corns, it does not keep them separated when removed.  Other toe separators such as "yogi toes" may make them feel better, however hammer toes are due to an intrinsic muscle imbalance.  Holding the hammer toes in a certain position will not make them "grow" like that or make them stay in that altered position.  The only way to change the position of hammer toes is surgical correction.  There are effective ways to decrease pain, such as strapping and padding that decrease areas of pressure.  And custom orthotics will prevent hammer digits from worsening, but also will not correct their position.