That should work, I like to use smaller sizes, not bigger then thumb.

Here is a link that might be useful: Konrad's modified bark grafting

any tips for a beginner? konrad, i have seen your grafting work and it is incredible and heals better than the grafts i have seen.

Grafts need light and growth will reflect the previous vigor of the wood they are put on. However if sun is introduced that wasn't there before, grafts on low energy wood may do fine.

Tips, don't cut it too close to the trunk,.. encase graft doesn't grow in about 2 to 3 weeks you can do it again the same season, if it still don't take there will be always another year.
You can keep scion in fridge for or at least 2 month.