Yes, the eido guaranteed gachas are probably one of the ways you can try to get those 100%s. The other being pulling when they put out those rate up gachas for all the 100% eidos.
Don't listen to the naysayers! They'll always say it's impossible. Instead, listen to your heart.
If you believe, you can make it happen. But first, you must believe in the heart of the cards!
And no, I'm not just saying this to try and get more 100%s available in the community.