I have no idea what I’m doing (Spectra S1)

I have been EBF and at 4 weeks PP, my pediatrician is recommending I introduce a bottle a day for my quality of life, sleep and eventual return to work.

I have a Spectra S1 and have NO clue what I’m doing.

At the first feed of the day I use a Haakaa to collect the first letdown on the other side; this usually yields a fair bit of milk. Then baby feeds 30 min and after she’s done I try to pump.

When I pump I don’t see any letdown, no matter what mode I’m on. I start in massage mode (C2 L2) and toggle to bacon mode (C5 L3) but never get any spray, just continuous drops on both sides. After 15 min I have about 1 oz collectively.

Why am I not seeing any letdown with the pump? Should I not be pumping after a feed? What mode should I start on and when do I switch? Is 1 oz a normal amount?