Other foods or supplements can either speed up, or slow down the digestion speed of your protein powder. High Glycemic Index (High GI) Carbohydrates and Sugars may help speed up the digestion and transporting of protein. Low Glycemic Index (Low GI) Carbohydrates and Fats may help slow the digestion and transporting of protein.
If you want fastest uptake of protein then either take it on its own with water, or add High GI carbs to the mix. In many cases, protein taken at the same time as any fats and slowly digested carbs will slow things down. In the case of Casein proteins, they're already very, very slow, so that will remain unchanged.