Currently the only way to make items not discountable is to open each individual item and check the box. There should be wizard and filter that would allow you to do this for an entire brand, or category, or department, etc. You should also be able to switch them all back to allow a discount.
The same goes for setting a BuyXGetY scheme - you should have a wizard that allows you to set up an entire brand or category for a BuyXGetY. Currently, you have to go into each individual item and set it up - which can take hours. Also, you should then be able to turn it off when the promotion is over.