I've only tried a fuel dot once. It wound up sticking on fueling and losing pressure in flight, all in the same weekend. And while trying to fix it discovered that a couple of my flying buddies didn't use them anymore. They'd had the same problems.

The hemostat actually isn't needed in every case. Depends on what line you're placing the T in. And how you fuel. My hand pumps put out pretty strong pressure and have no problem delivering full flow into the tank at the same time it merrily pumps about as much fuel down the other line off the T. I've got one plane with the T in the carb line. Even with my pumps pressure, fueling using that line doesn't flood the engine. Most needle valves restrict flow lots more than an empty tank resists filling (which isn't much).