Potty training help! Please

I am currently potty training my 2.5 year old and he will alert me when he has to go number 1 but he refuses to go number 2 in the potty. We are still using pull ups for nap and bed time so he will hold his #2 till those times. He also will go #2 at his Grandma’s house. Does anyone have any tips to try or different approach’s I should be taking?