It can be great fun to learn from packrafting or kayaking friends but you will gain a tremendous amount of knowledge if you take professional lessons and undertake a sequential training course rather than just receiving informal tips from friends. Remember that the biggest danger is that ‘you don’t know what you don’t know’ and this applies equally to your friends!
As mentioned earlier, one of the advantages but also one of the risks of learning whitewater skills in packrafts is that they encourage confidence very quickly due to their increased stability and ease of maneuverability. This can lead to a false sense of security as well as a lack of appreciation of the dangers of whitewater. I encourage all packrafters to deliberately and systematically focus on improving their technical paddling skills and river knowledge to avoid this. The American Canoe Association has some great information on these.
There are also now a number of packraft specific training courses that you can sign up for with quite a few kayak instruction schools also moving into teaching packrafting. Don’t aim to paddle harder rapids or more remote rivers until you have absolutely nailed the fundamentals on easier rivers. Focus on learning to paddle technically rather than on being able to simply get through and survive rapids. In an article I wrote for Hyperlite Mountain Gear I outline ten tips that aim to help you to become a more technically proficient paddler and since then I have now revised these tips further with information being available under Improve Your Paddling.
Luc Mehl offers one of the best bits of advice out there for packrafters, “If you really want to learn to paddle whitewater then learn to paddle a kayak”. The skills you learn from taking whitewater lessons in a kayak are completely transferrable to packrafting and will see your technical paddling skills improve dramatically due to the knowledge you gain from the reduced stability and the ‘edging’ characteristics of a kayak.