I've had my LGX 700 over 8 years. I've never heard the "duck call", though I have heard about it from others. For me, the inflation happens with each squeeze of the bulb and I don't hear anything.
Initially, the squeezing was very difficult - the bulb was new and more rigid then and my scrotum was sore and unused to being pinched. It was always easier to do in hot water and I even bought a hot tub to make it more enjoyable. I would squeeze the bulb and it wouldn't really flatten out all the way, but perhaps I wasn't pushing hard enough.
Now, from the first squeeze until the implant starts getting full, I can completely squeeze the bulb flat in the middle. I get about 15-17 pumps this way and then the squeezing doesn't go quite so deep. For about 3 more tries, I get partial depression of the bulb.until it's just clear that no more fluid is going in. I can still partially depress the bulb, but it really doesn't move and fluid.
So as far as point 1, IMO you don't need to hear anything to have the fluid moving, you just have to sense that the bulb is depressing. Little by little, as I do this, my dick pops up. Capacity for me is when I can't really squeeze the bulb enough to think fluid is moving. It's pretty easy to tell, though i sometimes try to keep pressing just hoping to get a little bigger.

As far as point 2, I was taught by my doc and still use an approach where I grab the tubes at the top of the pump between the fingers of my left hand, while pumping with the fingers of my right hand. Reverse for lefties, I guess. That keeps the pump from slipping between my fingers as I squeeze it. It's kind of painful to be squeezing hard and have the bulb suddenly slip out. With my left hand fingers on the tubes, they can push against the top of the pump (the rectangular block above the bulb) and the combination of hold on the tubes and blocking the motion from pushing backward makes it pretty easy.
I hope this helps. If you want to discuss, send me a PM or post something more here.
Best wishes,
Q.