The best way to help your fellow systems engineers get certified is to educate them about the value of INCOSE certification. They will show more appreciation when you explain the process, because SE’s love process, but what they really need is motivation.
Help them see the role of systems engineer like the parable of the bricklayers: you’re not just laying bricks, you’re building a cathedral! The systems engineer connects and translates and asks questions that lead to successful products.
Once they’re convinced that systems engineering is great, then tell them about the value of an external certification in systems engineering. Whether one has a degree in SE or has been doing it for years, a certification motivates them to gain perspective on the practice of SE and where they fit into it, and it gives them documentation they can use to help the world recognize them.
Finally, help them with the process. Organize a study group for the exam, offer to review their application, or host a paper exam.