Transplanting involves walking a difficult line between over-watering and under-watering. Remember that the roots have been damaged and are therefore unable to perform their usual function of water uptake for the plant.

Apply too much and you will rot the residual roots. You are trying to encourage immediate and maximal root replacement. If the rootzone is continuously saturated it will become anaerobic, cellular growth will halt, and say farewell to any roots. Apply too little and you will hasten the process of dessication. That's why an anti-transpirant buys a little fudge factor into the equation.

Definitely no fertiliser! This will create a zone of higher salt concentration around the root tips then there is in the roots themselves. Water will then diffuse from the roots into the surrounding medium in an attempt to balance the concentration. Yes, the plant will need nutrition to recover, but this comes after root initiation. For example, if I transplant during winter I cautiously fertilise in early October.

I personally think stressguard spray is a cop out as it is not proven to make any difference whatsoever but if it makes you feel better, use it! I am a firm believer that if your plants know you love them they will be okay... Excuse me if that sounds airy fairy, it's not meant to but I have experience in this area.

Make sure the new area you put them into is well composted with a NEUTRAL compost (not mushroom or another 'hot' compost) and use pelletised sheep manure if you can get it.... The main thing is the watering... Water them deeply (like 3 10 ltre buckets for t\rees and shrubs) a couple of times as this promoted deep new root growth....

Most perennials are very tolerant of being moved and should not be a problem.

let me know how you get on.