Dynomyco might be a better choice. Great white has a lot of unnecessary stuff in it. The only mycorrhizae that can colonize the roots of cannabis are endomycorrhizae. While Great White has those, they also have ectomycorrhizae, which can't. The species of mycorrhizae that actually has some evidence behind it would be glomus intraradices, which is in both products, the difference being you should be able to use less of the Dynomyco for similar results. It's also the same species of myco as what they put in Promix soils and media. I use Promix Organic blend. $10 Canadian for 28L (about 7 gallons for Americans).
If you're using compost you really don't need to supplement microbes or mycos, though. There will be some in there already, so long as you don't sterilize the grow medium.