Let me start off by saying and stressing just how important it is to index ALL of your backlinks. I have heard people in the SEO community say "Let Google find your links naturally". Nonsense. 90% of the backlinks never get found or crawled by Google without an indexer. I can vouch for this personally after building links for over ten years. Gone are the halcyon days when we could use a pinger to get Google to crawl and index backlinks. I am very shocked to see some popular indexing services use these techniques today. You may also remember when it was somewhat easy to index backlinks by submitting them to Google, completing a captcha and boom, the link was instantly indexed. I remember using a Lightning Fast Indexer which used many proxies and google accounts to basically submit urls to Google automatically one-by-one. This was a very expensive indexing method. But after Google has scrapped the ability to submit your url to Google manually, there are no definitive ways to index backlinks. Most online indexing services do not reveal their indexing methods but I am under the impression that they are quite primitive and best be left to the era of 2010.
I personally use the GSA SEO Indexer which in very simple terms creates redirect backlinks to index backlinks. I have been using this indexer with GSA Search Engine Ranker and the indexing rate is pretty good.
I can index your backlinks with Google by running GSA SEO Indexer for your set of urls. I run my indexer on a dedicated server with a premium VPN service with timed out IP change to get the best results. This indexing software is pretty good because it creates hundreds of DO FOLLOW and NO FOLLOW backlinks for every url and takes quite a while to complete which eliminates the need to "drip feed" your backlinks since the indexer is pretty slow and it achieves the same result as if you were to drip feed links to the search engines.
GSA SEO Indexer is pretty good for indexing most types of backlinks including web 2.0s, forum posts, wiki links, blog comments, articles, directory urls, social media links and many others.
To get started, I will need you to send me your list of urls in a notepad, one url per line. I will then the indexer on my server with your urls.
Generally, the indexing success rate is pretty good and mostly depends on the quality of your backlinks. Do consider things like content uniqueness, length, quality of the sites and other things.