As I've said before, despite claims made by others, it is impossible to go through every single bat in a large warehouse when on a Handpicking visit (Indeed GN actually store many bats away from Robertsbridge) especially if you are 'testing for performance' - these warehouses carry thousands of bats and there simply aren't enough hours in the day.
So in reality when Handpicking you aren't getting the 'best' bats, you are getting what you deem to be the best from the small selection actually look at. In this regard it doesn't matter if you get to go to a certain warehouse first or not, there are plenty of bats to go around. It's a nice feeling for me personally to be the first to open a box of shiny new willow, but it's not the end of the world if I don't.
Handpicking is very much an exercise centred around aesthetics, I fully admit that, unlike others. Classic example is the mid range bat that looks like an absolute dogs dinner but flies when you tap a ball up or hit it with a mallet. You won't see it it on the shelves of any retailer who handpicks, even the ones who claim to pick only on performance.........
Do I hit bats with a mallet/tap a ball up with them? Absolutely, because if I pick out a nice looking bat but it feels dead/unimpressive then back into the box it goes.
The main advantages of Handpicking?
I can filter out the higher end bats that don't look absolutely spot on (many people want something that looks perfect when spending £300)
I can hope (but not expect) to pick up some nice looking bats at the lower end of the range, I'll try not to take any planky ones but ultimately if you are spending sub £100 on a bat there is only so much you can expect, I always try my best though, haven't had any complaints thus far.
Any ropey looking or poorly performing (it's quick and easy to pick up on a bat that will be a dud in most cases.) bats can be avoided.
Form our point of view it's a good day out, nice to meet the people at the brands, chat cricket, view the facilities etc. in the case of GN we normally arrange for Chris or Alex to make a nice bat for our own kit bags too

Once all the bats are in the shop and a customer walks in, very rarely do I plonk a single bat in front of them, unless they come in with a specific model and weight in mind and are unwilling to deviate. Normally I ask for a few things to help narrow things down, then I start to lay out a few bats (anywhere from 5-20 is the norm I suppose, depending on the info they give on what they want) in front of them and encourage them to pick the bats up, have a swing tap a ball up and come to their own conclusion, I of course provide advice/input but the decision must be yours, you are the one who will be using it after all.