I don't get up to 1Dc, my largest upgrade (x25) before selling once I hit 5k shares is only 385No. (I run Judy and the 10 cheapest girls)

I probably do accumulate roughly 1DC total though, as I only have 4 upgrades that cost over 100No. This last time through took about 50 minutes, but I got pretty lucky with private shows.

My strategy is basically: If Judy has a private show, I upgrade her as soon as it comes up, ignoring all the other girls. (the first private show usually takes her to lvl 301 (if it doesn't, the second one does, which is 1 (x25) upgrade away from where I stop upgrading her.) If she isn't, then I upgrade all the girls with priority on the most expensive ones, until their next upgrade costs over 10No. At which point I save up for Judy's final upgrade, then finish upgradeing the other girls 1 or 2 more times, cheapest upgrade first.