What's the best treatment for a baby with teething pain? My 10 month old son has 2 teeth erupting at the same time and seems to be in great discomfort.

Cold teething rings. Cold will slow the transmission of pain messages to the brain at any age. For teething pain, I prefer a collection of several freezable rings that you can rotate over the day, replacing them as they thaw & refreezing. Medicines offer meager benefit & some problems. The teething gels last a few minutes & can set of some blood reactions. Benedryl can be applied topically but lasts only a few min.
Tincture of time. Fortunately the problem is transient...it will go away. A teething ring that can be chilled is soothing. Children's Motrin or Children's Tylenol (acetaminophen) may help...follow package directions exactly. Do not put child to bed with a bottle. Very important, schedule an appointment w a Dentist or (preferably) a Pediatric Dental Specialist to correspond w 1st b'day.
Cold biting ring. That is a lot going on in his mouth, first, liquid Ibuprofen or tylenol (acetaminophen) for pain. Next, let him do what he needs, biting or chewing on something cold, biting rings help the teeth cut and numb the tissue to make it late painful.
Cold and chew. Give them something a bit cold to chew on to help progress the teething and the cold can sooth the gums a bit. Some kids won't want the cold and you may think about a small amount of infant Motrin or tylenol (acetaminophen) if your baby is otherwise healthy. Do no give for extended periods of time. Know that these may only help and in most cases the child is still cranky. Rec he see dentist by age 1.
Let them chew. Chewing on something cold and firm is helpful. One idea is to give them a damp washcloth that as been frozen in the freezer to chew on. Commercial teeth rings that can be frozen are available as well. Teething is a normal process. I would avoid medication like painkillers unless absolutely necessary. Most babies really don't need them.