I try not to do this too often. I'd rather spend time finding better domains to buy. But some cases where I find this useful:

• Domain isn't in my niche and needs a little backlink anchor push in the right direction
• Domain is in my niche, but lacks link juice

I'm getting the most mileage out of separating my T1 PBN with 2 layers of Web 2.0s. Not only is it safer, but it yields the best result. (I've tried direct spam on the PBN, 1 layer of Web 2.0, etc).

Example:

Money Site < PBN < Web 2 < Web 2 < GSA Spam

Also, I don't use spun content at the PBN level. I'll use high quality spun articles at the first Web 2.0 level, low quality at the 2nd, and lowest quality at the GSA level.

Hope this helps.

I sometimes send high PR blog comment links (> PR 2), I have found using Scrapebox into the sitemaps of my PBNs.

so in other words their saying build manual tier 1 links to your PBN then link blast their tier 1s... blog < Tier1 like web 2.0 < GSA or similar.

You will ruin a good expired domain with spam links. Just buy good expired domains and you won't need to spam them.

Your PBN domains should already have good backlink profiles. There should be no need to "blast" them with anything.

If for some reason you're going to include a new, or PR0, site in your PBN, then I'd build it up by having a few "backup" PR3/PR4 sites used just for that purpose. As in, a PR3 site you don't backlink to money sites, but just put maybe a 6 - 10 backlinks on it to various PBN sites to boost them. But really, it's best to just initially buy strong sites for the PBN so you can forget about backlinking to them in any way, shape or form.

Don't blast quality domains with low quality links. You'll ruin the trust of that domain. What is Google going to think about a domain with thousands of spammy links pointing at it?