If you already weigh 285 pounds, you may not see any weight gain. If you weigh 128 pounds and are 6'2", you may be putting on several pounds a week.
If you are gaining now on 500-600 (which is it?), then I would not bother upping the dose. Just keep doing what you are doing so long as it is working.
Do you have a serious, planned diet, with a certain number of meals and protein, fats, and carbs planned out for the day? If you do not want to gain a bunch of fat, then control the diet. Eat cleanly. Add carbs as needed, but use clean sources, maybe easily digestible like Jasmin rice. There are 43 grams of carbohydrates in one cup cooked (although you can use the uncooked measure, that is tougher to do if you keep a bunch of it prepared).
43 x 4 = 172 calories.
So if you are already at 400 grams of carbohydrates throughout the day, adding another two cups of rice is another 86 grams and 344 calories, total is now 486 grams of carbohydrates and 1944 calories just from carbohydrates). It does not have to be all at once, either. If you are eating 6 meals, and you divide that extra rice up over four of them, that is only a half cup of rice per meal, which is not much extra volume at all to have to eat.
Try not to push your fats high. It is difficult when trying to gain weight, but you will be better off in several ways. Many report digestive problems when fats get too high.