My 2 year old is so picky. At the beginning he would eat only cereal dry and PB&J. I took a more old school approach to get him to eat more. I give breakfast and lunch and a small snack after nap attempting to ensure he's hungry by dinner, and so far it's worked. He's picking at his plates we serve at dinner but his eating has gone from cereal and pB&j to breakfast foods and fries, and chicken nuggets and even some meats! Good luck on your journey. But remember that they will eat when they are ready to eat. Maybe for the pedicure you could try flavored milk? Strawberry milk is a fave here and I should buy stock in hershys syrup.

At first you need to take him every Hour regardless if he has to go or not.
Congratulate him regardless if he urinates or not.
When he does urinate take note as the time-frame when he naturally has to go.
Routine is important.
If it's B.M. related, let him take a favorite toy, or play videos that he likes to laugh at while sitting on the toilet. laughter helps move the fecal matter.