I've tried indexing pins but sometimes still didn't manage to do that.
What I do is:
- use indexing services from marketplace (most have free trials);
- Make another pin linking to the pin I want indexed and then go to addmefast/like4like/youlikehits and get free shares of the pin linking to the pin I want indexed, so it make indexing faster as you can get 100 repins for free (not saying that you have to do 100 repins, I guess that 20 might be enough but more repins make it indexed faster in my experience, maybe start with 30/40 and it should index, probably, otherwise try with more).
You can do the same on Twitter, post your Pin URL and then use the sites for retweets and likes (10 likes and 20/30 retweets are usually enough) or also post pin URL on reddit (make your own subreddit and use it for posting links you want indexed).
One thing I noticed is that when you publish a pin it publishes on ALL the national pinterest domains, there are different pinterest subdomains for example for Japan, france, belgium and lot of other countries (sadly I don't remember them all of them). You can submit to indexing service the pin on those as well or pin linking to the pin you want to index there as well.
I had success indexing Pinterest board and I've seen that they're faster overall, and adding a section to the board makes indexing way faster for some reason, you might want to try it (I always submitted them to indexing services but for a board where I added a section it indexed in 3-4 days).
Hope this help.