Pooping problem

Good luck since they're older! Get a litter pan and put it somewhere that seems to be their most favorite pee spot. Place a different type of bedding in it and place some soiled bedding or poos in the pan. When they pee and poo in it and it gets a little gamey, change it immediately. Also, after one pees, place them in the pan and give them a treat. Hope this helps. They also might be like some pigs and are just like "Forget this man. Pssssssssss."

They have to have the want to train themselves. We can't make them go in specific areas. You can try litter pans but there's no guarantee that it will work.

Try putting hay in the litter pan. They'll spend a lot of time in there chowing down, and just let loose while they eat.

I know I trained my piggies with the corner style litter pans.
I use a wood pellet bedding with a layer of kiln dried pine or aspen on top.
I Place a different bedding inside the litter pan so they can differentiate between regular living quarters, kitchens and poop/pee areas. I prefer a product like yesterdays news in my litter pans, but just make sure its opposite of what your bedding is to make them notice.
Just as my best buddy DrawingWords stated, place a poopie when they go in there so they can see that they need to go in there.
Be patient it does take a while. Some pigs will refuse to do it.
I know my loner piggy was the one who was ant-litterpan. However once I got her a buddy she pooped in it the next day.
When you do floortime try to stay in the room a bit longer and if you wittness a piggy go in the litterpan give them a little slice of a veggie as a reward, I know when mine seen that they get a extra bite for pooping in a purple box, they actually will go over and make sure they stand in the box and wait to poop when Im in the room so they get a treat. LOL it's cute.
But there will always be times when they just cant hold it like everyone else and have a boo boo poo poo. So just take your time and praise and reward just like potty training a 3 year old.
It has worked for me and I think its helpfull.
Good luck!