Shave it for later. Tired of post-shave bumps, redness and those pesky ingrown hairs? TikTok dermatologist Dr. Samantha Ellis is spilling her secrets to banishing them — and it’s downright opposite to what you’d expect. TikTok dermatologist Dr. Samantha Ellis — whose viral clip boasts 342,000 likes — is spilling the tea, and it’s downright opposite to what your grandma taught you. TikTok / @drsamanthaellis “One of the first things I’m going to ask you,…