Repetitions with little weight is what all my previous trainers say.
Like using a regular size can of veggies instead of a 3 pound weight. Do arm exercises with the can in your hand. There are lots of them that work on the jiggly part of the arms.
If you do more weight and less repetitions then you build muscle. Fat can get trapped between muscles and be stuck. If you are just wanting to shape and firm up then do light weights and lots of repetitions.
For instance, every time you go in the kitchen you grab a can for each hand and lean a knee onto a dining room chair. Lean over a bit and pull your hand from the knee area back as far as you can. Like you're pulling on a lawnmower cord. Do that like 10-20 times every time you go in that room.
Every time you go in the laundry room you arm lifts, hips to where your hands are even with your shoulders then down again. You could go all the way up to where the backs of your hands meet over your head too. I love that stretch.
When you go into the living room you have a different arm exercise to do.
Keep a couple of cans of veggies in each room, you could even make them different so that you will remember with green beans you do this exercise and with corn you do that exercise. Just for some variety or fun.
Google arm exercises and then set your house up where you will automatically do your exercises.
I do leg stretches when I'm standing at the stove watching something closely. It feels good and I enjoy it. You can do all sorts of things in certain rooms.