First of all, I must say that I am not a vet. I can not tell you what you should do for your bird in his/her situation, that is a job for a qualified avian veterinarian. I am talking about birds in general and what is best for that majority of birds in bad situations.
I've been watching the Chloe Sanctuary videos
and they have had much success with the drug Haldol/Haloperidol when combined with environmental changes. I like the evidence based approach that the sanctuary applies. After making an an attempt to improve a bird's life, they track what was tried and it's effect. After working with a number of birds, the sanctuary has set of techniques to try, and some idea how often each those techniques are effective.
I know the consciences opinion of this forum is disfavorable towards the use of psychoactive drugs to stop birds from plucking. I would be too, if the idea of treatment was, "give a bird a pill, then put him/her back into the same old crappy situation". However, it seems to me that when combined with positive environmental changes, psychoactive drugs offer the best solution to a bird that was forced into a bad situation.
I have read many objections to Haloperidol, these objections are based on the birds being "doped out". However, many times such a reaction to Haloperidol is caused by administering too much of the drug. When a bird in the Chloe Sanctuary is placed on the drug, the goal is to use the minimum amount necessary to stop (FDB) Feather Destructive Behavior. In some cases FDB can be stopped and use of the drug is eventually ceased, in other cases some birds only require the drug during hormonal times of the year. Because of the minimal use philosophy, the actual amount given to a bird in a single dose will change over time. When given as minimal dose, many birds can spend there day in an engaged state and not be "doped out". This statement does not hold true for each and every bird, there are birds that do not respond well to Haloperidol.
Given the consequences of FDB when left unchecked, many caretakers are left with the only other choice of putting the bird in a restrictive collar or vest. In my opinion, birds in restrictive collars are worse off than the birds who are given drugs, because collars prevent so much movement that is natural to a bird. I understand that not every bird will be better off under Haloperidol. It seems that if collars have been the only thing that has been tried, and it seems that life long use is required to stop FDB, it seams reasonable that the use of psychoactive drugs should at least be discussed with a qualified avian vet.
The way the birds are dosed can be a major draw-back in real world situations. That is to say because people have to deal with life in general and deal with birds that giving the drugs to the birds can become "almost impossible" to do it correctly. The actual amount that a bird is given is constantly changing, because if this the drug must be given in a liquid form. A pill is not useful, because pills always gives the same amount of a drug. Once it is decided precisely how much drug to administer, a syringe must be used to measure it. This procedure must be performed once or twice a day. Missing a dose can reduce the effectiveness of the treatment. Because of the complexity of the delivery, there will be caretakers who can not mach the consistency needed, and I can understand those people not using the drug because of it.