Put the babystay away and forgetaboutit...Should you sometime find yourself beating in rough weather, and you see significant mast pumping. i.e more bend each time you hit a wave...then temporarily reinstall the babystay.
btw - re-reading your OP, but sure to use the lines with the plastic 'donuts' as guys, rather than sheets.. The donuts will prevent the shackle from possibly binding in the pole end.
Generally for the douse, we released the shackle on the 'tack' of the sail rather than let the guy run (as is normal on an end-for-end pole setup) This avoids the drag of the double sheet's/etc going around the boat. Releasing the shackle lets the sail fully luff, then now that no load is on the sail suck it in behind the main with the lazy guy and haul it on board. Most of the time we pulled it down into the forehatch. The neat thing about the double line setup is that you can take the lazy guy (leeward side) out of the blocks and take it where ever you need to go with it to pull the sail down. Another option is a belly takedown line, but your sail will need to have a bellybutton patch for that. This is a line attached to the middle of the spinnaker, then you release all three corners and quickly drag the sail below using that line. We never used it.. it's another line hanging there all the time that's likely to cause a problem at some point.
Be sure to manage/control the release of the halyard, don't simply blow it. Whoever's on the halyard should be watching the proceedings and feeding the halyard at a rate that the crew can recover without letting the sail go into the water.
As SF said, 5-10 knots true is about the minimum to practice.. any less and you won't have enough apparent to easily fly the sail... in the beginning, over 15 knots true will make managing things dicey if they go badly.
As I was frequently reminded, generally speaking most of the snafus during gybes and takedowns can be traced back to the helmsman and the "quarterback" calling the shots.
Once you get it all right, though, it's really rewarding.