The best time to utilize carbohydrate supplements is post workout. Carb supplements like waxy maize and vitargo are rapidly digested and assimilated. That makes it optimal for post workout to quickly replenish depleted glycogen levels.
Taking the carbohydrate powder pre-workout is not ideal because it will make you become hypoclgyceaic during your workout.
Pre workout - you want to stick with slow digesting low glycemic carbs because they will give you sustained energy throughout your workout. Before my workout I like to mix a whey isolate shake into oatmeal with some natural almond butter
Post workout - you want a easy digesting protein source and carbohydrate source to quickly replenish depleted amino acid and glycogen levels in the body. I would use 60g of whey isolate + 40-80g of waxy maize or vitargo as a post workout shake. Around 90 minutes later I would eat a high protein, high carb, moderate fat solid food meal.