Why are you pumping? If baby is nursing great, then don't worry about increasing supply! More is not better, as long as baby is getting what he needs (pees and poops, gaining weight), relax and enjoy your baby! Pumping is not a requirement of breastfeeding (lots of moms breastfeed for a year or more and never touch a pump) unless you have a particular reason.
If it is to increase supply, then you would be doing it after baby nurses (baby is always best for stimulating suppy) and the point is to increase stimulation, not to necessarily get out a lot of milk. If baby is nursing great, then don't worry about increasing supply! More is not better, as long as baby is getting what he needs (pees and poops, gaining weight), relax and enjoy your baby!
If it is to store up supply for going back to work, you may want to wait awhile before working on that. Let your body adjust to lactating again, get used to having two children, and enjoy your baby. When it's a couple weeks before you back to work, then start building up a freezer supply.
If it's so someone else can feed the baby, remember he may not be taking more than a couple ounces per feeding so huge quantities aren't needed. You may find it easier to just nurse the baby rather than pump, clean parts, clean bottles, etc. Have dad bring baby to you at night and nurse in bed, then have dad lay baby back down, change diaper, etc. You still get lots more rest. You'd probably have to get up during the night to pump anyway because your breasts would be full!
Information below about correct pump flange sizing is good. A good lactaction consultant could help with this.
Good luck and congratulations on your baby!