Grist's first loyalty ability by putting a loyalty counter on it, causing you to create a 1/1 Insect creature token and mill a card, and then put a loyalty counter on
Grumgully and repeat the process if the card was an Insect.
The Insect enters the battlefield with a +1/+1 counter on it due to
Grumgully, causing it to have
Grist's abilities.
Repeat from step 1 using the Insect token instead.