Let your boss know exactly what's happening. I would explain it just as you have here. Let your boss know that when you ask for help you are dismissed and told to find the information yourself. I would tell your boss that you care about efficiency and find the current mentor reduces your efficiency via their methods. Explain you do not learn best in the environment you are currently in and since you wish to work at your fullest potential within the company, you wish to have a new mentor to facilitate this. Good luck.