Set policy. Like, you have a list of recommended software. I'd say at least two browsers and a bunch of utility software. You support those, and beyond that it's best-effort. Curate the collection. With a clear idea of what's in use, you can even start to assemble the whole thing from FOSS and eventually move to a non-proprietary OS to underpin the tools. But that really is but a side-effect of having a good grasp of the needs of your shop. See the LiMux project.
Communicate. Not just this one thing, your entire policy, FAQs, tips and tricks, what-have-you. An internal website will do. A wiki is great for this*, even if you're not opening up editing to others. But you could do that for selected parts too. Make sure everybody knows where the fount of (IT) wisdom is to be found. You don't have to be pushy about getting people to use it; even helpdeskers reading ready-made solutions to panicked people is better than having them making up answers on the spot, though this is only true if the ready-made stuff is of good quality. And if it applies to the situation, but that's the helpdesker's job to workout. So make a point of both having helpdeskers add questions and of curating the material, so you both know what's popular and that they have decent answers.
Most of all, don't get condescending; write *for* the reader, not *at* them, or worse, refer to them as "the user", like so many programmers do. Who're they writing their software for, anyway?
Once that's going you can even expand into short tutorials**, book reviews to help pick up more skills, and so on. But let's get the basics going first.
Notice that if you have your shop organised with ready-made software and information answers, people will have a well-known point to look at in case of panic. So with that in hand, in case of big trouble you can send out word with a recommendation to review the latest news in the usual places where all the details can be found, with a short abstract with enough information --accessible to them-- to let them make a "should I spend time on this now? can it wait until later?" decision.
Don't try to force people's hands until and unless absolutely necessary. Give them the tools and the right information on the right time to let them make meaningful decisions. This requires not so much serious writing skill (though it helps), but putting yourself in their perspective. "I don't understand all this, why do I need to bother?"
* Plenty wiki software available. I like dokuwiki and dislike mediawiki because syntax, which I think is important as it is a tool to express and so convey the message. At minimum go for CREOLE support.
** A tutorial isn't a tutorial unless it also tells how to recover from mishaps. Most "tutorial" blogposts fail at this and as such are not worthy of the name.