I used Buttercream Dream not anticipating 75% humidity in Va this week. My octagon cake is now too soft and wont hold clear lines, so it looks more like a messy circle.

I'm planning to scrape off all the buttercream dream and use the Wilton recipe or something. Is there anything else I should do to make sure I get clear crisp lines?

This is so hard to describe but place your offset spatula on one side of the area you want a sharp corner on and slightly push away from the corner then put your spatula on the other side of the corner and once again push away from the area. Another trick is to place the cake in the freezer then after 15 - 20 minutes take it out and heat up your metal spatula under hot water and continue as instructed above - butting up to the corner and pushing away from it instead of dragging the spatula over the corner.