I a new here, but have had alot of experience since a child with small animals,
So if you are holding them and they get ansy, I start having visions of that commercial "gotta go gotta go gotta go right now", so put them in the litter area you want them to go in or the cage, where ever.
Not saying that will be big help on training, but I have only my second piggy in my life and my first was never potty trained and this one is still a baby so I dont know if you can really get a piggy trained. My rabbit on the other hand, all actually have been trained to atleast go back to the cage to pee.
You should see my 4 year old chasin dropping all over with her little hand held broom and dust pan, she does most that cleaning up!