I only NOFOLLOW affiliate links, and apart from that, don't worry about the rest of them, internal or external. Sometimes I have multiple links to an URL, most times I don't. Whatever makes sense for your USERS. You don't need NOFOLLOW links for SEO purposes (and whoever gave you that impression is no "expert")
Don't worry about PageRank, for cripes sake. That and a dollar won't get you a cup of coffee.
I'm not an expert link builder by a long shot, but I am absolutely convinced that one of the reasons my sites and my clients sites succeed is that I link out, freely and without worrying about it, wherever it makes sense to do so. My standard rule is if the link will enhance the user experience to some significant degree, then I add it - dofollow. That said, I am pretty picky about who I will link to - they have to provide value and authority. And guess what? A bunch of 'em notice and link back, without my having to ask. Some don't, but that's ok too.
I'm pretty sure that's how it's supposed to work. And it does.