I used to try to fill the bl00dy thing with the riser tube in, but it just gets in the way. You try to get the thing in as far as possible, but before you know it the lid gets in the way.
Now I'm not so paranoid about packing the resin in, and this has the added benefit of being able to shake the vessel when the tds starts to rise - not so easy with 18l of wet resin.
I toyed with the idea of using an old, smooth, lampshade with a slit to do the funnel trick, but never got around to it. I just heap the stuff in with a glass.