Orphan cockatiel air crop

Hi. Am new to this forum. Yesterday a friend of mine called me and told me that he have a baby cockatiel his mother died ( stuck in the cage and a cat cut her head ) she was feeding the baby and the owner doesnt know how to hand feed i have had two babies cockatiel back in 2017 and i succeded to hand feed them although some problems.
Sorry for this long introduction.
Main reason am here this baby fear my hand whenever i try to feed him second he have some air in his crop the more i feed him the more air he have. Once happened to me in 2017 and i gave him boiron carbovegitabilis 9ch and it worked so should i do it again or there is another solution?