Okay, technically not speedier training, but faster at getting a colonist to a Native Settlement and to their ultimate destination: make them into Scouts! If you have horses stored in a settlement, making a Free Colonist into a Scout will get them to a Native Settlement and then to wherever you need to send the Expert faster. This is especially helpful for the rarer Native specializations like Silver Miner, often their settlement is far from your own settlements. This is especially good for establishing a new high-food settlement, as not only will you be able to get to the Native Settlement and new area faster, but you'll also get a load of horses in your new Settlement without having to use Wagons that you can use to build new stables!