1. Get the pumpkins off the ground. I used the plastic milk crates.
2. IMHO you have to, must, manually pollinate. Take stamen from plant A and liberally douse the pistils from plant b.
3. I never let more than a single pumpkin grow on one vine unless sub 20 pounders then two.
4. I used MiracleGrow like it was free.
My soil prep was to dig a square hole in the ground minimum 2foot on a side. Remove all rocks, clay, sticks, and replace with dirt, compost, 1/4 bag of cheap 13-13-13, and then as much top soil as necessary. Water weekly. I wanted a pyramid-like mound. Did all this early spring. Come late June NLT July 4, Square off the top, plant 4 Seeds NESW, and if you believe in it (My Dad did), only in the dark of the moon.
Since it is close to too late, about only thing you can do is manually pollinate. Then, pinch off blossoms that take and only allow one or two per vine.
I have a pic somewhere. My pumpkin leaves were over two feet long and about that wide. The hairs on the leaf stalks were sharp and stiff, enough to jab you like BlackBerry thorns almost.