Activate the Forest or Island by tapping it, adding ({G} magic symbol) or ({U} magic symbol) .
Cast Earthen Arms for its awaken cost by paying ({6} magic symbol) ({G} magic symbol) , putting two +1/+1 counters on Gilder Bairn, and causing the Forest or Island to become a 0/0 Elemental creature that is still a land, and putting four +1/+1 counters on it.
Activate Experiment Kraj using the Forest or Island's ability by tapping it, adding ({GU} magic symbol) .
Activate Experiment Kraj using Gilder Bairn's ability by paying ({GU} magic symbol) and untapping it, doubling the counters on target permanent.