i have to pull the iron quickly before the solder fully melt to create a bridge, once they are fully melted, the hope to make bridge will diminished dramatically.
Yeah, this. On a QFN, it's nearly impossible to make a bridge that you can't just wipe away by going back over it. But with gull wing leads, like on a QFP, there's a tipping point where too much solder on the iron allows solder to wick up into the shoulders of the pins and bridge/blob. The shape/size of the iron tip affects where the tipping point will happen. Technically, you could wipe the tip clean and touch it to the fluxed bridge and pull a little solder out of the bridge. But with a pointy conical tip this could be highly impractical, requiring 10-30 go-arounds and plenty of re-fluxing. With a 2-3mm bevel tip, you can be a lot more sloppy with how much solder you use, and if/when you cross the line 1. this tip works great with solderwick, and 2. you can often just touch the tip to the solderwick and then used the cleaned tip to suck out many bridges, rather than using the solderwick directly on the pins. Or you can lay the solderwick next to the pins without even touching, and use the bevel tip to bridge the gap between the pins and the solderwick. So you don't really have to worry about solderwick freezing to and pulling on pins.
I think a common mistake for people who haven't soldered fine pitch stuff before is thinking that because the pitch is fine, the tip should be small. That's not the case.
+1. With a bevel tip, in particular, the size of the cut face is important. And up to a certain point (around 2.5-3mm), bigger is better. The cut face of this tip acts like a solder reservoir. The fuller/rounder the solder bead hanging off the bottom, the more solder it wants to leave on a given pad. The more empty/clean, the less solder it will want to leave (or the more solder it will suck away off a full pad). So the larger the size of the tip compared to the size of the pad, the bigger your target for how much solder to load it with, and the less the tip will change over time as solder is deposited to the board. It will just keep chugging along.
There is a similar effect for many tips shapes, but the bevel has one of the strongest effects because the cut face where solder hangs down is round and tends to wet out very easily/fully.
The shape of the bevel also can get right into 90 degree corners, like on a QFN. The rim is sharp/crisp, and depending on the angle you go at, you can get an adjustable edge/wedge angle anywhere between say 45-90 degrees on a bevel that is cut to 45 degrees, for good thermal contact onto the side pad and the PCB pad. The round shape glides over pins without catching and it also acts like a preheater, giving the most heat to just one or 2 pins, and getting good preheating on the surrounding pins. Whereas if you place a big chisel or knife along the pins, you are outputting potentially huge amount of heat along that entire area to get the solder to flow.
If you have a Hakko, you can even try the CF bevels, which are only wettable on the cut face. The entire sides of the tip are chromed. The bridge sucking effect is way more dramatic with these tips. They are way better at drag soldering and essentially just as good or better at any SMD soldering other than QFN, IME. And because solder doesn't wrap around the side, the beads maintains a relatively small surface area, which keeps the solder wet the longest between refreshing with flux or new solderwire before the tip "dries out."
IME, the dedicated drag soldering tips with the hollow face (spoons, well tips, also called gull wing tips) are gimmicky and don't have much advantage over regular bevels. OTOH, they have reduced thermal transfer due to the hollow. So you generally have to bump up the temp, and the tip dries out faster.