Douglas Fir is a difficult wood to stain evenly. A 50|50 mix of your Exterior 450 stain color and Exterior 450 Clear would be a better choice for an exterior conditioner. Blotching may still occur even with this procedure.
After applying the conditioner mix, let it dry 2-3 hours. Allow more time in humid weather. Then a apply the stain color of your choice. Multiple coats will deepen the color.
Watch Exterior 450 Topcoat Overview Video Here
Watch Exterior 450 Stain Overview Video Here