I'm growing out some rootstocks in a nursery bed setting -- they are from last year, all propagated via cloning (some just natural suckers that were removed from the parent tree and moved into the bed, and others purchased from a nursery), some apple and plum. Some were of grafting size last year, and I grafted varieties onto them in the spring, but some of the grafts either didn't take or didn't make it through our brutal winter. Now these previously grafted rootstocks have put up new not-yet-lignified shoots. Others, I never grafted onto because they were far too small for me to comfortably graft onto -- 1/8th inch or smaller, and they are not much bigger now, though they are not new growth and are lignified.
My question is this: how do I get these shoots to size up for grafting? Obviously, where two or more shoots exist, I'll select the best shoot and prune off the others, but beyond that...? Just let them grow until they are big enough (that was my tactic last year, and the plums particularly, really never sized up adequately)? Head to stiffen? Should I leave any lateral shoots on the leader/trunk, for added photosynthesis, or should I pinch off any elongating lateral shoots that form? Any advice would be much appreciated.