I have never been a witness but may start to study soon - just to keep a channel open to my lifelong friend soon to be baptized. I feel dishonest, but if he thinks I'm a potential convert I might stay close to him and gradually reveal the truth about the truth (all learned from Bible, past Watchtowers, Books & Internet over past 5 months.
Could never do that myself....
Just brace yourself for the reverse of what could happen. As you reveal the "TRUTH" about "the truth" your friend could just as well brand you and apostate or bad association and distance himself from you anyway. You may find that the time you studied to have been a total waste if it comes to that.