Setting up the correct area is very important with swirling, as it is with most things. But given that the things required to swirl are all watery, paint and messy things then the requirement for preparation is more.
You will need (summary):
Other stuff you might need
Firstly you will need paint, I use Humbrol Enamels as they seem to work very well, this is not to say other paints don’t work but if you use other paints the borax mixture or water temp may affect the paint differently. The matt and metallic paints don’t seems to work very well so I would say to stick to the gloss paints until you get it right before trying the other types. Also buy at least two pots of the colors you want to try, nothing worse than opening a pot and realizing the paint has dried up.
And don't forget the primers, you will need a white primer primarily. I then use a satin/matt undercoat if I want to have a base color. Base colors change the color of the swirls so best to stick with white until your happy with the swirling technique and want to experiment with colors,
Get this from the tap, just don't assume it will rise from the ground on command, you will need to make sure there is a tap nearby.
This must be large enough to allow a guitar body to be placed inside, preferably at least 1.5 to 2 times as wide as a guitar to allow movement and at least 1.5 times as deep (its difficult to hold a guitar underwater so the wider /deeper it is the less chance you have of the guitar moving and hitting a side.
Something like this is best. Its a good idea to not get a black container, the lighter the better really so that you can see the colours clearly.
Borax (Sodium Borate) is usually found in the household cleaning aisles. It has many uses but the one we need it for is to break the surface tension of the water to allow the paints to disperse evenly across the water.Depending on where you go the price changes. I buy mine from eBay but you might ding it in a local store which is always handy (no waiting time for delivery). You will probably need about 3-4kgs to start with as it takes a lot of practice to get this right (and a lot of water changes).
To start of with its best to use test wood, you will probably want at least 5 or more bits (similar to the one show) because you don't want to have to dip and then wait for the paint to dry before you can respray and dip again. Anything will do for test wood, I have used all sorts (even used a flower pot when I ran out of wood); but find bits of laminate flooring very good and cheap.
You only need this if your dipping an actual guitar body, it will need to replace the neck so that you have something to hold on to when dipping. Anything which fits into the neck pocket and can be screwed in place will be fine.
Just something to fill any screw holes so water doesn't get into the wood.
And don't forget newspaper, have plenty of it ready. You need it to clear the remaining paint off the water surface and to cover anything you don't want to get paint on.
Having a rail of some sort is very handy, when swirling I usually drill a hole in the handle so that I can feed a wire trough and hang it up. Also if you do this it is much easier to spray the guitar in the first place. They are usually only about £10-15 so fairly cheap for how useful it is.
Paint gets EVERYWHERE so using some latex gloves is a very good idea.
Of coarse you will want to video the final dip for prosperity (and to have it on this site for others to see!!)