The clubs have agreed the outline of a €20m deal with Gremio to receive 15% of his next transfer fee.
Only the final details of the operation need to be sorted before it can be made official.
Everton is a special request of returning Benfica coach Jorge Jesus and part of a big summer for the Eagles.
He was initially valued at €30m but the pandemic and other factors have brought his price down.
Gremio own 50% of his economic rights with the other half belonging to businessman Gilmar Veloz (30%), his previous club Fortaleza (10%) and an investor (10%).
Everton has bagged 47 and assisted 17 goals in 179 appearances for Gremio, leading their scoring charts in the last two seasons.
The talented attacker has been capped 14 times by Brazil since 2018, scoring three times.