Do you have a heater? I had the same problem for the last few days; my betta had swim bladder disorder and was floating sideways. I fed him peas, fasted him, added salt, did water changes... nothing worked until I put in a heater and it resolved itself in hours literally.
I've read that the correct temperature benefits their metabolism since cold water slows down these processes; by implication, proper temperature probably helps other important functions as well.
EDIT: And to answer the title of the post, I use a tooth cleaner aka waterpick (http://www.craniorehab.com/assets/im...vedsyringe.jpg
) which is essentially a syringe with a really small 'neck' so it picks up little pieces of food great and it's not as dangerous as skewering the pea and risking injury to the fish. I think it's available at most pharmacy stores... if you have the pea bits submersed in water, the waterpick can pick it up easily