https://www.bestmaterials.com had a huge resource of listed materials and the installation instructions for each item are at the bottom of the item description if you select that specific item.  Simply search for the specific flashing.

Other resources

https://www.oatey.com

Masterflow GAF Lead Boots

https://kozykollar.com/installation/

https://www.bulletproducts.com/bullet-products/

https://permaboot.co