Hello Jay,
I just started grafting some weeks ago.
I use fresh cuttings,cut from own plants on seedlings,i think non rooted cuttings are better as they are in growing state and not rooting state.
I used only the green parts,no leafs only small claws,or just simply cut the leafs off.
I used one older cutting (woody) on a wooden sidebranch,its connected good but is sort of dormant.
The others (6) all grow new leafs.
If your big plant has nice branches you can put several colours on it.
It took around 2/3 weeks for the graft before i removed the tape wich hold it on its place,and i use V shape cuts.

greetings,Michael

Thanks Michael. My concern is that I am going to prune down lower into larger diameter trunk. It's unlikely that any cutting I order will be as large for an exact or even near exact match. Do you think the graft will succeed if this is the case?

Hello Jay
Even if the graft is put on a thicker branch it will stick as long as the cut (bark) fits one side into the V shape and the rest is covered by tape,or that special graftpaint ?
Example: If you cut a main branch straight(horizontal),you can even put 2 or more cuttings on top,In holland they call it crowngrafting,only in this case its a side branch.
The lenght of the cutting is lesser important,better smaller than larger,but try to use the green part as that is the growing state.

succes!

Thanks!