Go to your photo on either the photostream or the photostream/lightbox page of flickr. (I much prefer the lightbox view.)
Highlight the html address, right click and copy.

Go to this forum, set up a new topic, but instead of uploading the photo, right click and paste the copied link.
The photo will show up on the forum post and when clicked on the viewer will go to the flickr page which is at much higher resolution. I usually add a comment to "Click on image for higher resolution".

I have been doing this for some time and really like how much better the photos look with more resolution.
I'm not sure that it is significantly easier, but the result is much better.