Choosing a linear regulator vs. switching regulator for low-power application?
I believe I may need a buck-boost however, because the components will
  need at least 1.8 V and 3.3 V, and my 3.6 V battery could drain below
  that


First hit on Linear Technology might be useful: -




Try going to LT to get an idea and use this parameter search engine.


  for the 1.8 V rail it's 1.154 mA


Use a linear regulator - it's just not worth the effort I believe to use a switcher from 3V3 to 1V8. However, if current was over 50mA I might start considering a switcher.

Generally, you can assume a buck regulator will give you about 90% power efficiency near full load and a buck-boost will be about 85%. Ball-park figures.