For a top fill tank use in this order for a bottom fill reverse the order.
Put about 2 ml of Buttercake juice in the bottom of the tank. Then very very gently put about 1ml Berryyum floating on top. Close and vape. Treat the tank very gently do not shake it up or tilt it too far over. Keep it upright as best as possible. You will get butter cake juice vape and then after a few vapes the berry will start showing up and get progressively stronger till it’s all berry kinda like eating a layered dessert.
both recipes are out there.