Um, got a pumpkin? Pretty quick to puree it down. Cut into chunks, zap in microwave, and mash or stab blend. If you want to use the other pumpkin you mentioned, stab that down too or pass thru a sieve. Not familiar with any squash that wasn't baby, but I don't see why you can't. Different flavour is all. Just don't know how it would taste.
Too many restaurants, not enough time...