What I have been doing is buying my spices in 5 Quart jugs. Then I vacuum pack them in smaller bags. You can then either freeze them or not. Then when the 5 quart container is empty, I add another bag. That way I can shake them up real good and get rid of any clumps may may develope. That said many bulk spices will have anti-clumping agent tossed in.
I love montreal steak seasoning on steaks and burgers. I am not too sure it is best for brisket though. I don't believe it has the right amount of sugars. But if that is the flavor you like, you go for it.
But in my honest opinion Studly, you are not using enough spice. If you are not comfortable with the cayenne, stay away from it, but run with something else that might work for you.
This whole cooking thing is my hobby. I have two dinner parties a month. whether it be cajun/creole or bbq or seafood. I enjoy it and my friends do too. I always experiment. I know what works but I will slightly alter my spices and see how my friends react. I can go out to dinner with my family and spend $100 or I can cook for my family and friends for the same and get leftovers to boot. Plus the quality is better, plus I like to show off. So far my ST has been quite the toy to brag about. Last weekend we had a rib roast (choice) from COSTCOS. We had 15 people for dinner. Nothing was left over. There were even about 4 people there who had never had rib roast before. Mainly because they do not like their meat rare. Well I made believers out of them.
So experiment with your smoker and your spices. I will send you some spices. I have been shipping out spices to folks on this forum since I joined a few months ago. Email me your address and I will send you something to get you out of your box.
This first image is where I have dusted the brisket with the cayenne. I normally go rather heavy with the cayenne, but this is a new brand that is supposed to be twice as strong. Well in the end it wasn't. If you want to use cayenne, but do not want to chance it being to strong. just mix it 50/50 with some paprika for the ease of an even application.
This second image is where I added the garlic powder. You can also use garlic salt, but depending on what else you are going to apply, you may not need any more saltiness. As you can see the garlic powder is absorbed rather quickly in that you almost cant see it. Again, how much you use is up to you.
In this third image you will see where I have applied the commercial rub rather heavily. As you can see I have given all it can take. Even now it will not all stick to the meat. But I will do my darndest to rub as much as possible into the meat.
This fourth image is my brisket completely rubbed down on both sides. I prepared both sides alike. I did not wrap the brisket in the foil pictured. I just transferred the meat here for the picture because once I flipped the brisket over to apply the rub to the other side, things on my cutting board got rather messy in a hurry. Also after I applied the rub, I made sure to massage it into as much of the meat as possible, hence more mess, but a good mess!
I always prpare the fat cap side last. That way when I set it on the grate prior to going into the smoker, I will not disturb the rub as much.
This final image is where I took the brisket out of the smoker once the temp got to 160 or so and then I chose to wrap it and place it back into the smoker for the final cook to 190 degrees. That is not necessary but what I chose to do on on this occasion.
So as you can see, in order to get a good flavor from a rub you need to apply a liberal amount said rub/spice. This is important as well where a good bark is desired.