I also posted at 6 months about how often I was feeding DS. Between milk and solids it seemed like a permanent food fest.
Can you focus time wise on the milk feeds to get them in the right place for DS2's routine and then just offer him solids at the same time as the family/DS1's meals? At 6 months he doesn't need to have set solids meal times, just tastes and experiences with food, it doesn't matter if he doesn't take much either, just joining the family at the table and tasting one or two things is enough.
How about BLW so you don't have to make separate puree foods and spoon feed? It's a great experience, just alter your cooking slightly to chop foods into larger batons, cook without salt/sugar/honey and then you can pop anything on DS2's tray and just let him have a go?