Why do you think you can’t use dormant buds from last years growth? I kept my scionwood well over the winter and used some buds to do a multi variety plum tree a week ago. The rootstock was pushing and the bark slipping. That should be possible, doesn’t it?
Given a choice I would recommend other technics in spring, cause I like the vigor, the stability and the the look (not a very convincing argument, I know) of eg. splice/whip and tongue grafts better. But in this case budding was handy to do the multi variety tree.
I knew I read about it. There @Stan speaks about spring budding. Maybe he can contribute about possible disadvantages?