I'd really love to try this. And to be honest I think it would be easy enough to do. I've seen videos of pigs being milked and they do thrust at first, but then they seem to just be fine with relaxing while they dribble and squirt for a while. Plus if you got a pig young and got him used to hand jobs then you could let him breed your dick frequent;y enough to have him stretch you out.
As for the gel plug and getting into your bladder, I have no idea. My guess would be that a little pee and some sounding would get most if not all of it out. I'd also like to imagine that the plug has a natural tendency to dissolve in urine, I base this on the idea that nature seems to do things this way and if a sow got her urethra plugged it could kill her, so it seems like a logical evolutionary trait.
Take this with a pinch of salt as I only have basic knowledge of these kinds of things so I have no idea if it is accurate. Maybe I can fond out first hand one day though.