Apple grafting:. Two questions

[Beersmith]

In February I reported that I had some M27 rootstocks and I was waiting for warmer weather to graft scions from St Edmund's Russet onto the rootstock. In the event things didn't go too well, only one of the four attempts took.  However the rootstocks were strong and soon developed more strong healthy shoots.

So in summer I tried again. This time chip budding Queen Cox buds to the rootstock. Now all these grafted buds took well and look very healthy. So the next key stage will be in spring 2019 when I will prune away the growth above the bud and it should - hopefully - grow away to produce three new apple trees on my chosen M27 rootstock.

But an important question. When in spring is the best time? Early spring? Late spring? Do I need to wait for the grafted bud to burst? Or wait until the rootstock buds swell? Does it perhaps depend on temperatures or does it not matter at all?  Any advice would be most welcome!

Second question. The thread was started by ACE who was planning to graft Howgate Wonder scions onto another apple to create a type of family tree. How did it go my friend? Well I hope!

Cheers

[Beersmith]

[Obelixx]

No personal experience but the RHS has this info on chip budding - https://www.rhs.org.uk/advice/profile?PID=400 - and just says spring.