If you can get some training from Master Tam on this someday that would be best. You are essentially correct, however, in that the techique comes down to directing and filling the lower dantian and the middle warmer with qi to avoid hunger (i.e. locking the stomach).
When we put people on the pigu fasts we usually have them come to a Tong Ren class weekly to repeat the locking. Also, while they are on the fast, they are often taught the Tai Chi Dao Yin routine. They will perform this routine everytime they are hungry. After performing the routine they are rarely hungry. The fasts, however, can be full or partial and of varying lengths depending the patient, their reasoning, and their overall health so each persons experience is different.