I REALLY like omega's OYL-605. It's a blend of plantarum and brevis, with plantarum doing the bulk of the work. 1-liter starter, no hops in the wort, pitch at 90 and within 24 hours you can expect to be at pH 3.5 or less. It's very hop intolerant, so keep them away from your wort! At least until after souring.
If you can't get that blend, look for something that contains plantarum, such as good belly probiotic juice or tablets.
You can keep a culture of Lacto going for later use - just buffer it with some calcium carbonate to a pH over 4.0 to keep the bacteria healthy.
I've stopped boiling after souring - just pitch your sacch or brett in with the bacteria. For me, boiling is an unnecessary step unless you want to hop the wort for whatever reason.
