One thing you should always do is figure the number of growing days and then make sure your starting date is going to get you at least 90 days of pumpkin growing after pollination. Depending on which weigh-off the pumpkin goes to, if I pollinate around June 24th, that gives me 92-99 days until the weigh-off. Must pumpkins will stop between 90-100 days. I have had a couple grow 105 days before however. Weather, genetics and plant health can become key factors for how many days you can get.
In the pots I use ProMix BX soil-less potting soil along with some beneficial microbes, azos and myco. I'm going to do something this year that I haven't done in the past. With each watering, I'm going to put just a very small amount of water soluble fertilizer. The plan is to tell the plants that there is lots of food available, right from the start, so the plant will beef up and be ready grow.