Brett has affiliate programs for his Salesletter Software (previously B.U.R.P.I.E.S. copywriting software) which is managed via Clickbank. So if you don't already have a Clickbank account, please join up with them first. There's no cost to register to become an affiliate.
Once you've created a Clickbank account click on 'Marketplace' (the link's at the top of the page) and then enter "salesletter software" in the search box towards the top and click on the search icon next to it.
Brett's SalesLetter Software should show as the top result with the title of "New Salesletter Software Makes Copywriting Easy". Click the Promote button for this product and it will ask for your Clickbank Account Nickname so you can create an affiliate link.
He also has an affiliate program for his AudioWiz software, also managed through Clickbank.
You'll find a link to join Brett's AudioWiz affiliate program on the following page:
You will also need to have a Clickbank affiliate account first to promote this product as an affiliate.
Although Brett isn't able to have an affiliate program for his book as it's purchased through a publishing company, it is sold on Amazon.com. So you could register as an affiliate with Amazon.com (https://affiliate-program.amazon.com) and promote Brett's book as well as other Amazon products.