Just follow the tutorial you posted:
Here's a really cool PhotoShop tutorial for liquid filled glass text. Would be nice to have a gimp tut for it.http://psd.tutsplus.com/tutorials/text- ... xt-effect/
The only major difference was in the contours for each layer style setting done in PS. The Layer Effects script/plug-in does not have the identical set of contours. So when doing this tutorial, instead of log, try half round.
Forgot to add, that rasterize in GIMP works differently, since you can't right click a layer and select "rasterize". To do this in GIMP, create a transparent layer beneath the layer needing rasterized, then right click that new transparent layer and select "merge down".
To get the second level light glare shown in the PS tutorial (Layer Effects didn't have triple ring, so I used double ring), I shrank the text path a few pixels and added a white stroke (about 2px) then blurred it 8px. That could probably be improved a little, I just intended to get through the tutorial to see how complicated it would be.
"In order to attain the impossible, one must attempt the absurd."
~ Miguel de Cervantes