The more you do it, the less time it takes, I used to be superslow, but once you get some practice. 16 isnt really a whole lot, especially if you used to be a multie.
esepcially in the start-up phase...have a country open in each tab and do the same thing in each country...explore xx amount of turns each country, build xx buldings in each country, etc. Usually cuts the time down...also for buying/selling...use the economy tab on your control page as much as you can. to mass buy/sell goods.