I'm not directly working on spam, but it seems like there's a heavy reliance on ipv4 address reputation these days, which is probably one reason mailservers won't use ipv6 any time soon.
In the last years though, I cannot really recommend to use any of the DNSBL anymore. I've encountered more cases where legitimate servers were blocked due to netblock vicinity or indeed previous ownership than actual spam issues.
Greylisting will still catch dynamic allocations almost as effectively, while you won't reject legitimate mail due to server and/or DNSBL issues.
In other words, if at least two DNSBL queries agree, then reject, or feed this information to the rest of the spam pipeline?
I found this to be pretty much worthless if you already have greylisting, even for high-quality curated lists such as spamhaus SBL/XBL.