http://steamcommunity.com/profiles/76561198025518010/screenshot/542897863359240770
That was my first ever blue mushroom farm, if you have a melee weapon with long range, such as the Blade of Grass or the Murasama, you can get all of the mushrooms very easily. I used a similar layout for my normal mushroom farm, except after every row of dirt, I put a row of bricks underneath. This stops vines from growing and stopping the growth of mushrooms on the next layer down.
I'd visit that farm every now and again, usually it'd be chock-a-block with mushrooms. Usually around 550 or so. My normal mushroom farm was slightly smaller, and would only produce 5-10 mushrooms per visit, because of weeds hindering the growth of the mushrooms.
Mud blocks are affected by gravity now so that wont work anymore. You need to put stone or dirt under each row of mud tiles.