<human>: Can you give me a shortened version of the text?

Hi, this is my first time posting in /r/dogs and I was hoping to get some advice. My mother and I had a 2 year old KC Spaniel/Pomeranian (Lucy) since she was a little puppy, and we recently adopted a 3-yr old male Shi tzu/dejon from the local humane society. Lucy, I got to know over time and I always know what she wants, and how she is feeling just by looking at her. (happy/sad/playful/jealous/concerned/empathetic/excited, pretty much anything) I can usually even tell what she's, generally, thinking. I can read her so well I always know what she wants.

With Samson, our new dog, he is much more difficult to read. Hid body language seems to have ambiguous meaning to me. He gets freaked out sometimes if someone else pets him wrong (usually not with me though), and sometimes he barks terribly if attention is suddenly drawn *away* from him. Overall I have difficulty understanding what he is feeling. I understand that rescue dogs often have emotional baggage and I'm totally ready/willing/able to work through that with him over the course of months, but it would be greatly to both of our advantages if I could comprehend him more.

Back info: He was an owner surrender; owners said due to their own health concerns they could no longer take care of him. We have had him for about 1.5 weeks, I take him and Lucy on walks every day, we feed them once/day the suggested amount for dogs their size. He was very overweight when we got him but he lost 1LB since then (now he's 17.5LB)
<bot>: What can I do to enable myself to read my new adopted dogs body language more efficiently to gauge how he is feeling emotionally?