Bowing the pack, never thought of that. The sharing of info always contributes to knowledge.

Me I face the old pack, towards the part that rides my small back. Grasp the sides or handles and hoist to my knee. Then slip my right hand/arm into right shoulder strap. Bend ever so slightly to let the pack come to rest upon my back. Then slip the old left arm in , make some adjustments. Off I go. Its an old backpacking technique.

When shouldering a boat: a little momentum generating bouncing off the thighs can help. The old bridge technique can help too, as can the deck rest...the former is how I built the strength to shoulder the Chestnut solo back in the day; I only had maybe 30-35# on that barge.