If your rootstock is strong and vigorous, preferably beginning a new vegetative growth and you prepped your scions by removing leaves and letting the scars heal your grafts have a good chance of taking. Of course it also depends on your grafting abilities as well but you seem eager to learn and your asking questions on the forum to better your chances. Please keep us updated on the progress of your grafts.
When I get failed grafts, I like to unwrap them to see what possibly went wrong. Sometimes I just make sloppy cuts and the cambium didn't heal over. Other times there is some callus tissue forming but the graft just didn't take for some reason, I usually attribute these failures to weak rootstocks.
Simon
I prep the scions while they are still attached to the tree. Prepping the scions significantly increased my takes. Whenever you make any cuts on a scion, some sap will ooze out, drying it out a bit but not much. By removing leaves before you cut the scion off, the rootstock is able to refill the lost fluid but more importantly, when you remove the leaves from the attached scion, you remove the chemical signals from the leaves that inhibits new flushes. By removing the leaves, the tree sends signals to the now defoliated scion starting the cascades of signaling reactions that initiates bud growth and ultimately a new flush.
Simon,
How about prepping the rootstock as well, at the same time when we will prep the scion? May be that signaling effect will start here as well to initiate new growth and there will be increase of fluid flow that will speed up the healing process?