I know it's the end of summer but this really was a sensational shrub when Rhubarb was peaking. I used the Cold Shrub method: no cooking but the shrub has to stand for a longer period of time before it is strained.
Found the recipe here (but it's a cooked shrub): http://www.seriouseats.com/recipes/2013/04/homemade-rhubarb-shrub-recipe-vinegar-syrup-for-drinks.html
Here's a great article about Cold Shrubbing: http://www.seriouseats.com/recipes/2011/06/cold-processed-berry-shrub-recipe.html?obref=obinsite
2 lbs of Rhubarb cut into approximately 1/2" slices
1 Cup White Wine Vinegar
1 Cup of Turbinado Sugar
-Combine ingredients in large mason jar and shake it until the sugar has dissolved.
-Shake every day for the next 3-4 days.
-Refrigerate shrub after the 2nd day.
-On the 4th or 5th day, strain the Rhubarb out and transfer to a new jar.
-Shrub will keep for 4-6 weeks.
I've used this shrub mostly with Gin though I think it would work well with Blanco Tequila or White Rum.