Dylan
I have been using the "PCB fab in a Box" materials which use a special paper for easier toner transfer instead of dry or wet resist and UV curing. But it also includes a 'green foil', elsewhere sometimes referred to as "TRF" Toner Reactive Foil. This material goes through the same laminator that is used for toner transfer and causes the green 'foil' to get stuck on the toner. This makes the toner, which is in reality lots of little blobs mostly melted together and therefore somewhat porous into a more liquid tight trace. It is possible that the green foil can also be applied to the resist for the same function and cover and tiny gaps due to creases in the original dry or wet applied resist or dense spots in the paper or printout that shade some spots just enough to cause the resist to not fully cure.
If the last problem is your main source of trouble, you might also try over exposing the resist to the UV until you start seeing swelling of lines and potentials for bridging, That might help the UV, and thus the cured resist 'spill over' into filling those really tiny gaps.
Hope this helps. But as I said, I have not tried resist based pcb etching, so I am only guessing there.
Mike