Pre Shave oil question

Hey guys, been wet shaving now for 6 weeks and have been curiously obsessed with it, but that's great because I'm not a morning person and its helped me wake up much more. Ok, I use an Edwin Jagger DE89L and due to purchasing a blade sampler I've narrowed the blades down quite a bit; Feathers, Astra, Polsilver and most Gillettes work very nice for me, But...even with Feathers I find it tough to go against the grain under the jaw and chin line. I prep very well with a warm towel 3 times/30 seconds, been using AOS Lavender and EJ best black badger brush. My beard is like barbed wire in those areas especially. Do you think a pre shave oil would help or any other ideas, or am I just doomed to not be able to go against the grain in those two areas without irritation.

Thanks guys