Yep as everyone has said there is a huge amount of technique to get going right at the low end. You need to get that good initial scoop/pump to gain enough board speed and hence apparent wind to make the subsequent pumps worthwhile. There there right near the flight envelope pumping the foil plays a part.
I'm going to be honest though if it legit nothing more than 8kts it's going to be hard work even on super efficient foils and race sails. You are right at the absolute bottom end of the range, you can't point and just flying is tough. 10kts+ and things come alive

Gusty conditions it's a different story because it's much easier to fly through a lull that actually get flying in one.