Since I've got it working on my installation now, here's a quick overview of the steps I took:
b) create an app/assets/javascripts/comfortable_mexican_sofa/application.js.coffee file in my app
window.CMS.wysiwyg = ->
$('textarea[data-rich-text]').each (i, element) ->
$(element).addClass("tinymce")
tinyMCE.init({
selector: 'textarea[data-rich-text]',
menubar: false,
plugins: "link image code",
toolbar: "undo redo | cut copy paste | styleselect formatselect | bullist numlist blockquote | bold italic | removeformat | image | link | code",
convert_urls: false,
content_css: "/assets/newpub/style.css,/assets/newpub/discoveryfont.css"
});
I'm not sure that adding the tinymce class to the textfields is necessary (I don't think it is with the selector provided in the tinymce init), and obviously some of the config options are a matter of preference in a given application, but overall the installation was quick and mostly painless.