I dont think arm fat is any sturdier than the fat on the other body parts.
I had a similar problem at the beginning of my weight losing mission - and here is a useful tip for you, I picked up from my ex trainerīs ebook
swivel your arms in circles while they are in a horizontal position. Start with small circles then go big do this 3 times a day for 1min.
Worked for me, so give it a try