Congrats on the Rainbow - they are a fantastic (looking) snake. I got one from a guy two months ago and was told he was a bit aggressive, etc and was wary of him when I first brought him home but he has been great to handle. I am always fascinated by how smooth his scales are (compared to my other snakes, especially the Jungle carpet). And he is fast - when he wants to go somewhere (where I don't want him to go) he can motor! He likes to wrap around my waist and then slide down my leg to get to the floor - caught me off guard the first time he did that as I thought that I was dropping him.
It is definitely fascinating to feel the difference in scale textures between different species for sure. My Kenyan Sand Boa almost feels scaleless. He's just so smooth. And my Brooks king is the total opposite. Big thick bumpy scales.