Exhibitions are the single races that you can start from the race routes on the map. There are 63 in total, and you need to fully upgrade each festival for every one to be unlocked.You don't have to win the races to unlock this achievement! Only complete them.
You can shorten the amount of time it takes to get this achievement considerably if you use the blueprints. When editing them, select "race options" and set the time and weather to a clear day (if it isn't already). Most importantly, if it's a circuit race, set the amount of laps to one.
You may want to switch cars depending on what surface you'll be racing on. A supercar may be the fastest on the road, but on an off-road sprint you'll be spending half the time rewinding because it bounced everywhere and went off course into a tree.Note: there is a known bug where every event shows up gold but the achievement stays at 98%, view this thread post for a possible fix ---> All exhibitions achievement ?