Flywrench

I made 100 planets that are as easy as they can get. Subscribe to them all at once here: http://steamcommunity.com/sharedfiles/filedetails/?id=714397129

This shouldn't take more than 10 minutes.

EDIT: A much easier method to unlock Blissful Soothsayer has been found, see Cuttyflame's guide.

My original, outdated guide:

In my experience, the fastest way to unlock this achievement is to simply send friend requests to Flywrench players and ask them to play your planet. Be sure to mention that they shouldn't play your planet in easy mode, as these players will be put on a separate leaderboard and effectively do not count towards the achievement.

However, if you don't want to ask people to play your planet, I have also created a popular collection of 100 easy planets that people use to unlock Exoplanet Addict (Beat 100 User Planets in Time Trial). If you have created an easy planet, send me a message on Steam or Discord and I will replace one of my levels in the collection with yours. By doing this, every future achievement hunter that plays through my collection will also get to play your planet.