There should be advice with the prep. For two days before eat little fibre. So, rice, potatoes, white bread. Nothing with seeds. Nothing red. Chicken or white fish. Drink plenty of fluid, fruit juice with no bits. Stay near a loo. Enjoy the brown pencil.
For 24 hours (or whatever the instructions say) eat nothing solid. You will be hungry...
It’s best to over follow the instructions, nothing worse than the endoscopist cursing and setting up a new appointment for you… (my notes have a note to say one kind of prep should not be used on me, it doesn’t work)
I’ve had about 15 endoscopies, not kept exact count… only had Picolax once, last week. It was like the starter for the main corse of Moviprep.