K.,
I have just begun to potty train my 2 year old twins.
So I really don't have much personal experience to share, but I do want to share what all my friends told me, who have gone through potty training many kids.
They had the older kid go with the little one into the bathroom and praised the older kid for doing his or her business and washing up properly.
Eventually the baby wanted to copy the older sibling. Get the older kids to encourage too.
They also had a sticker chart on the wall and everytime they went on the potty, or at least tried to stay dry, they got to put a fun sticker on the chart. After 3 or so, depending on the age of child, they could earn a reward.
good luck.
I will be in the same boat as you soon, and I have no older siblings to help, haha.
T