I brought these two trees into the greenhouse about two weeks ago. In fear that the cold would kill them. It got down to -10 -15C over the last few weeks. I know I could easily loose them because they are still in pots and were never planted in 2019. The buds are starting to show and may be a few days away from opening. The nectarine is right behind it and I might bring the peach in soon just to get a head start. They will all be planted at the end of May when it warms up outside.

My question is, Can I use a paintbrush to pollinate these trees?

Here is the Apricot