Udon noodles are bigger than 'normal' noodles and so are a bit heavier to pick up. What i generally found when eating with chopsticks was, if you positioned your hand at a certain length of the chopstick it was easier to pick up certain things. For general eating holding the chopsticks at medium is normal, for heavier foods i found that holding the chopsticks a bit closer to the food helped picking them up easier (so possibly try that for Udon noodles). I find its best to eat rice when you hold the chopsticks much further away and close to the top.

Just my general insight of it