Those small attachments work. I misplaced my set when we moved, and I'm still looking for it! Meanwhile, I have been using painter's tape to tape a straw to the end of my full-sized crevice tool. When you use a small opening like this (either a straw or the mini attachments), you want to put your vacuum cleaner on the lightest suction (if you have the option of adjusting suction).
I do not think it is ever a good idea to blow air into a machine's innards, although some people use canned air very judiciously -- aiming the air above so it blows out the bobbin cover opening.