you should purchase them AFTER you launched a kickstarter campaign. BUT,you should mention to them about what you are planning to do BEFORE you start your campaign. That is so they can advice you if theres a good period to do email blast.
for example, if theres currently 5 projects selling watches who applied to use TGF services, is it wise if you, also selling watches, to use their service at the same time? because?
imagine you are the customers. the email/promotions/offers receiver.
you need to choose between 5 watches. now, the chances will be reduce to 20% for your success. right?
you should check one of my posts "1 year 7 months of research compiled"... its a summary of all the things i've been researching for crowdfunding marketing for my last job. so it should help.