Currently there is no way to make finding a legendary faster. To unlock legendaries in the first place you have to beat all the gyms in the region that the legendary is from, for example if you wanted to get a Mewtwo you would have to beat all the Kanto and Orange Island gyms then go to Fungal Cavern to find Mewtwo, for Galar legends you have to beat the gyms in the P.V map. For Vortex legends, you have to beat EVERY gym. (including Galar) Hope that answered your question.