My elastrator prongs have a wee indentation about half way along; this is where the ring should be for application, then roll it off / pull the closed elastrator out once the testicles are bagged.
Linda, I do it almost exactly as you describe. A few things I would add, though. First and foremost is, before you even get the elastrator out, is to make sure that you can feel two healthy normal plums and that they are fully dropped - coming away from the body with an appreciable 'stalk' that you can visualise getting the ring around. I agree that if you do this in a heavy-handed way, the testicles get retracted and you can't nab 'em, but if you do it quickly, gently but firmly you shouldn't scare them away.

From which you can conclude that I
do handle the sac and I don't find that that means I can't get the testicles - but I am now fairly experienced as I have done hundreds every year for the last 7 years and I guess I have learned how to handle things so that the plums don't leg it back into the body.

And the other thing is that I expressly
do not press at all on the teats or behind - a very experienced farmer told me to never do this as it could cause some intestines to be pushed through the ring as well as the testicles. So I place my fingers firmly on the teats but do not press, and I almost dig the prongs into the body as I slowly and gently allow the ring to close, kind of scooping the testicles up into the ring as I do so. 87% of the time, you can see both testicles filling the sac before you have the ring fully closed. I then check that I have both testicles before I pull the elastrators away from the ring - this means that if I am missing one or both, I simply open the prongs wide, remove the device and start again. If you do this without excessive handling you can usually get a second try - mostly if you fail the second time you better let him go and come at him again tomorrow.

When the testicles are both there, then I hold the ring steady with one hand and pull the elastrators back and away with the other. And then I check again that I have two testicles before I put the lamb down.
Like many, I do balls first then tail, so an undocked tail means 'testicles present' - but if I didn't need that visual cue, then I would do it the other way around, so that I can give lambie back to his mummy as soon as I've snared his balls. However I guess that since the lamb is sitting on his bottom on your thigh, he could be sat on his smarting tail ring, so perhaps it is best to do the tail last after all.
