There are few tools to do.
If you are working on mass spam, then I would go with scrapebox / Xrummer as you can blast for millions of millions of websites in no time. I am not pretty sure those are even worth it for most niches. But some black hat niches are definitely worth it. I don't think you will need an auto-approved link list with those tools.
If you want comments from good sites that can get indexed with time and still need to pass the ranking signals, I would opt for GSA SER and buy a good link list. It's not hard to find many blog comment link lists, as many contain those engines. So you can opt for something cheap like LinksPlug, and GSAserlinks, which sell all kinds of blog comments. But if you are using those links in some somewhat quality manner, enable filters like OBL at least 30.
If this is a quick project only with comments and you don't care about spamming things, just outsource it for a few bucks. That way, it's cheaper.
If you want quality and don't need millon of links which is recommended just use a software with goold link list