If you want to make tomato sauce, the way my Nonna taught me (at this time of year) is to use a Vittorio strainer, which is a food grinder thing that ejects the pulp and juice one way and the seeds and skins another.
Quarter the whole tomatoes and leave them layered with salt in a cheesecloth lined peach basket over night to drain some of the water. Cook them until they are squishy (with some onions, celery, maybe a couple hot peppers), run them through the strainer, cook down more..