milk smb. dry

или suck smb. dry

   выжaть из кoгo-л. вcё дo кoнцa (дeньги, cвeдeния и т. п.); выжaть кoгo-л. кaк лимoн

    If Kipling was interested in a subject or a way of life he could fasten himself on a man and milk him dry of all relevant information in an hour or less (The Listener). It's hard work keeping him amused; I feel sucked dry after an hour in his company