Cultivating rootstocks for bud grafting

A short question to the experts:
I’m currently in the process of growing bare rooted rootstocks of Rosa canina ‘Laxa’ for a later bud grafting procedure. I normally buy them fully cultivated and developed shortly before grafting. This year I wanted to try the pre-cultivation for myself, so I am still unsure about the best and correct procedure. After potting on 20.04.2024, the sprouting has started immediately so I have well formed foliage up to over a half of the shoots from above. It would be helpful for me to know, how I can push also the sprouting on the low eyes more efficiently to achieve finally stable root growth. Can tweezing help or is simply more patience needed? Many thanks for any recommendations.