its a very very old school of thought, which unfortunately gets passed down and recommended to mothers of today even though all the new evidence suggests that not only is it unlikely to work, but that it can actually do more harm then good.
Some babies sleep through from an early age, some don't. some do and then hit the 3/4month growth spurt, regress to waking a couple of times a night and take months to go back to sleeping through again.
Ask in the weaning section, there are plenty of mothers in there that will tell you that weaning and giving solids didn't change sleeping patterns at all. Some just take longer to not need as many night feeds, its really only after 6months that its 'medically' recognised that they don't 'need' night feeds so at 2months old I wouldn't be to concerned, your baby is just doing normal baby things.