Bottling from 1 gallon jugs sucks. I used to do it all the time, but I came up with a much easier way.
When I did bottle from a keg, I used one of the mini-Autosiphons with a bottling wand on the other end. I used a carboy clip (or whatever it's called) that clips to the Autosiphon to set it right above the trub. The biggest PITA was getting the siphon started while pressing the bottling wand down. I'd end up in all sorts of contortions trying to get both started at the same time. Once the beer started flowing you could bottle one-after-another rather easily. I primed each bottle individually, since I never really knew what my yield would be. I mainly use the Coopers carb drops, but I have measured individual doses of sugar if I was out. The carb drops have always worked for me, but do leave you with a higher carbonation (maybe between 2.5-2.7 volumes).
Now I simply rack into a keg and use that as my bottling bucket. I push the beer out using a low pressure of CO2, and still prime the bottles individually. It is so much easier. If I didn't have access to a keg, I think I'd rig up a small bottling bucket out of a 2 gallon bucket. Bottling straight from the jugs is more hassle than it is worth.