Modulating cortisol is more about lifestyle changes than anything. Some supplements can help. Rhodiola ( https://biotest.t-nation.com/products/rhodiola ) for example is a great product to help your body handle stress better. It should be taken in the morning.
ZMA ( https://biotest.t-nation.com/products/zma ) about 45minutes before going to bed (or even prior to that if you had a very stressful day) is very good addition by helping you sleep and recover better.
Then you have all the products that have anti-inflammatory effect... inflammation, especially chronic systemic inflammation from constant heavy lifting and eating a lot is one of the biggest possible stress your body can have. Reducing it will thus lower cortisol.
The two best products for that are Curcumin ( https://biotest.t-nation.com/products/curcumin ) and Flameout ( https://biotest.t-nation.com/products/flameout ).... these two supplements should actually be used by everybody conscious of their health.
Finally you can do fwhat you can to reduce cortisol release from your workouts. Remember that cortisol is increased during training for a reason. It doesn't just go up when there is stress and do nothing, every hormone has a function. Cortisol mobilize stored energy during training. Basically it will pull out glycogen from muscles and fatty acids from body fat and make them available to use for energy during the session.... sadly it can also breakdown muscle into amino acids (catabolism).
Now if we look at what I just said... if you make energy (carbs) readily available in the bloodstream while you are working out, there is less need to mobilize stored energy and as a result cortisol doesn't go up as much. That why a peri-workout protocol like PLAZMA containing easily absorbed carbs will help reduce cortisol release during training.
Post training or at night you can also use glycine (up to 10g) and vitamin C (no more than 1000mg) to help lover cortisol a bit... glycine is a neurological inhibiter ... it stops your brain from spinning too much when you get home, preventing you from relaxing... glycine helps you put the switch to OFF which reduces the stress.