I agree with Lemmy, It is often thought you need a needle fine tip, but the reason it doesn't produce enough heat is that the air cools the tip too quick. If you are soldering to any sizeable trace such as a ground plane, this cools the tip and solder as well.
Probably the best tool for soldering monoliths is nothing to do with solder... it is a Stereo Microscope. Once you can see properly, the soldering becomes a lot easier.
Tips:
buy some very good solder. I use a multicore type, 60/40 alloy, 5 cores (r cores of flux inside) AU$25 for a large roll of 250Grams
drop a small amount on the monolith to make an upside down cone shape, not too much. Tin the wire if possible, or clean the end of the wire with 1200grit sandpaper, as this is the area the most trouble, getting the solder to stick to the wire. I also use a flux pen on the monolith and wire end.
Look at the soldering iron you have and measure the tip length and inside diameter, then look on ebay for a compatible tip.. there are 2 main sizes IIRC. Then get the longest and thinnest. Don't sharpen your tip ar the coating/tinning that protects it will be gone and the copper underneath will just get wrecked in a short amount of time. The tips are pretty cheap and I have been getting at least 3 months out of 1.
keep a wet sponge while soldering and I also dip the tip in a tub of Soldering paste also got from ebay or Jaycar.
There are some monoliths with no real pads, just traces and tiny Vias. These are a real pain no matter what.
I was bidding on some wire bonding units, Manual Wedge Wire Bonder, Kulicke & Soffa 4123, used to bond wires at micron level to ICs.. but The price went too high
http://www.evansclarke.com.au/detail.asp?id=746212