When contacting them, try to stay neutral and basically just pointing them to something interesting that is worth talking about. If you "ask" too much, like as a favor, it sounds too much like if you're looking for free advertisement. Sure, we do want the advertisment, but it's a very well worthy news.
Another thing, albeit a bit harder, is to try to recruit developers interested in building modules for the wallet. You don't necessarily need a developer who's sole goal is to create apps, but most of the time you could get some people to want to have an app relating to their service created (like how api is used everywhere). Some examples are news websites, exchanges, pools or price checkers.
You can also inquire people to add the simple yet amazing "click to send" addresses on their websites for easy donations and payment.
Furthermore, tweeting and stuff about it and trying to get those tweets to high followers count people in the crypto field is easy to do and can enlighten a lot of people to Particle.
What's really great about Particle is that it sells itself, you don't need to hype it. You don't need to lie or exaggerate or have to get into elaborate marketing schemes. It's innovative enough that the only thing it needs is people to be aware of it. The rest should be viral.