I don't understand. You should just need to do it once to load the font and then it should be available in the wiki.
"For reference copy 2. Specify in CSS into another tiddler."
You can see a demo of that here: http://googlefonts.tiddlyspot.com
Of course, you can use whatever font you want instead of the two here, you can add more or delete any.
Tiddler:
$:/font
Tag:
$:/tags/PageTemplate
Text:
<head>
<link href="https://fonts.googleapis.com/css?family=Acme" rel="stylesheet">
<link href="https://fonts.googleapis.com/css?family=Allan" rel="stylesheet">
<style>
body {
font-family: "Acme";
}
h2 {
font-family: "Allan";
}
</style>
</head>
EDIT: Formatting. Also, I removed the <head></head> html tags and it still worked, but I'm leaving that here.
<link href="https://fonts.googleapis.com/css?family=Permanent+Marker|Zeyada" rel="stylesheet">
And that's the content of my rawmarkup tagged tiddler. (fonts have been deleted from the above for brevity).
The thing I did, wrongly, is to try to play around with the tiddler I created $:/tags/RawMarkup. I wanted to include a comment to tell myself what I did. As soon as I did that, it broke stuff. So... ok I guess I can't explain in that tiddler, I'll explain in a tiddler leading to it. A bit messy, but no big deal. $ tiddlers are not meant to be self-explanatory anyway, they are code.
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<!-- To be tagged with $:/tags/RawMarkup -->