If you think your beardie may have MBD, you would be better off with the full strength liquid calcium you can give orally instead of the spray on type.
One of the moderators here, Tracie(Drache613) has a website
http://www.bug-de-lite.com/ She sells the liquid calcium at a very good price and can give you exact dosage amounts for your beardie depending on his size and severity of MBD.
Tracie will answer any questions you may have for she is very knowledgable when it comes to bearded dragon illnesses.
You can either PM her or go right to her website with your questions about the liquid calcium.
Hope this helps!