When it comes to Guest blogging - A Good Mix of both do-follow & No-follow links is best!
For example :
If you planned to publish 1000 words on 1 Guest blog.
Just split them into 2 x 500 words with 2 article titles.
then, Ask the blogger to publish two articles, need do-follow & no-follow links.
Like first 500 words with 2 contextual links.
1 link points to money site (do-follow link ) & another link points to the other post on same blog, but published it on different dates i.e no-follow link.
Explain it to blogger & Bargain the price!
I've tested this with couple of my own projects & it works greater than what i expected!
If you focused only on building do-follow back links, then it looks unnatural to the eyes of Google. But the Good Mix of do-follow & no-follow links will brings Great SERP Magic.