I actually have a tube of penetran. It is used for people with arthritis. Exotics vets have used it with parrots with skin disease, which is why I have it- for my parrot's feet. Cross beak is typically not due to any skin disease- but a malformation of the beak due to genetics or early damage. It's use in cross beak is probably related to the pain of the condition- and to help relax muscle spasms related to the pain of having the TMJ joint progressively damaged by the growing beak. It may help relax the muscles around the face/TMJ joint to allow the beak to return to a more normal position- AFTER the beak has been trimmed. Many of these birds with long standing scissor beak (24 weeks is long standing) have permanent damage to the TMJ joint, and trimming will help the bird eat, but the beak will never be normal.
The harsh truth about these guys is that this will be a lifelong commitment to trim the beak every 2-3 weeks. Most do not grow well and will die even if you try to stay on top of the beak's growth. They suffer from malnutrition and usually starve to death. They LOOK like they are eating- they are hungry and peck at things often, but they cannot meet their daily calorie requirements without really aggressive hand feeding (or tube feeding). Most people cannot do this. I hear time and time again about these guys who struggle for months, and die around 4-5 months old from not getting enough to eat.
Help for the bird with cross beak is trimming often and aggressively, finding out what they can eat (try crumble, pellet, wet mash), feel the crop at night- and if it is not full compared to the other birds- it is not getting enough to eat.