Tom, yeah I've never done enough electronics work to justify one of those variable temp irons - my soldering tool collection is rather sparse too. A 40 year old Sears 25W chisel tip for wires and a 15W/25W conical tip from The Shack for the occasional fried resistor/diode/transistor, etc., some 60/40 rosin core and a roll of Chemwick. The chisel tip works better for wire joints since it has a lot more surface area available and can dump the heat more quickly. Plus it's much easier to balance some molten solder on the flat of a chisel tip than on a cone!

Rick, you said "finally" but it really shouldn't take very long for the solder to flow after you hit it with a hot, wet iron. Think of the end of the iron as a repository of heat - you let the temp build up and then you have a certain mass at a certain temp and (in the short duration it should take to solder 18ga wire) it's almost irrelevant whether the iron is 25W or 40W - all that matters is the temp differential, the mass of the hot body, and how well the heat can be conducted. You can't do anything about the mass of your tip so to minimize heating time (maximize heat transfer) you work with the other two variables - let the iron get good and hot, i.e., give it enough time to heat up initially and let it recover between joints - this will maximize temp. As for maximizing conduction, you already know about using a dab of molten solder to help transfer heat. There's not much difference in the temp of a 40W iron and a 25W iron it's just that, given the same mass, the 40W iron will recover and be ready to solder the next joint more quickly.

Now, if you've got a small iron that doesn't store enough heat to solder 18ga wire then you're relying on the output of the element itself and yeah that will take a while. Need a bigger iron if that's the case. But I doubt it. Never seen a 25W iron that wasn't physically big enough to solder 18ga. The bigger the wire, the more heat it sucks up thus the bigger the iron required. Bigger irons have more mass to re-heat so need more power to get back up to temp in a reasonable timeframe and once up to temp they dissipate more heat so need more power to maintain temp.

Yeah, I know blah blah blah - OK I'm done.