What a wonderful grandmother you are to help your grandson with Zoo-phonics! I'm assuming that he enjoyed working with the tutor, learned a lot, and is eager to discover more. If he knows all 26 signals and sounds, then he can teach you. It would be a marvelous way to re-enforce his knowledge and build his confidence. Then you and he will share your own special way to communicate.
The two of you can do it together or with the video that's in my article (there are also many more on youtube). Remember to move through all 26 signals and sounds every day. This is key. You want to master these so you can then move forward and make words.
Since your grandson is going in first grade, he should learn to make CVC (consonant-vowel-consonant) words with his Zoo-phonics signals and sounds: dog, cat, jam, kit, nap, win, sit, pat, bat, set, lot, pet, hug, fit, bug, hat, pig, etc. He should be able to do these quickly and efficiently. These are the building blocks for reading, writing, and spelling.
Once he has mastered CVC words, he should move on to making blends with signals and sounds: bl in blot and black, ck in clock and kick, spl in splash and split, and str in strict and strip. These are challenging but fun. He should also work on digraphs (two letters that make one sound) such as ch in chat and chick, th in that and this, sh in shelf and ship, and wh in what and whip.
When my son was little, I purchased the “Zoo-phonics Parent Kit” on zoo-phonics.com It included a manual, an instructional DVD, a music CD (that we listened to a whole lot), and alphabet cards. I thought it was well worth the money, and my son loved it.
With Zoo-phonics you want to keep it light and fun. Don't hesitate to be goofy. Kids learn so much without even realizing what they're learning and how much they're learning. When I volunteered in second and third grades, I dealt with many kids who never mastered their letter sounds. That's never the case with kids who are taught Zoo-phonics; they have it wired in their brains for their lifetime!