To sour milk (if you don't have buttermilk), pour 1 tsp of vinegar or lemon juice into a measuring cup, then fill to required amount with regular 1% or 2% milk - despite it's name, buttermilk is not a high-fat milk. Let stand for 3-5 minutes to let it sour - if you do this first it will be ready when you are done mixing your dry ingredients.
These scones freeze well - let cool completely, then freeze, individually wrapped, and reheat in the microwave for 45 seconds or as needed.