Cheers, Simon - all good stuff. If you think that one type is 'thinner' than the other, then I'd use that one for getting into tighter spaces like the inner/outer panels seals, and the thicker one for coating exposed chassis members and wheel arches, etc. Mind you, it all dries very quickly to be like 'candle wax'!
In response to a 'private' enquiry, here's more detail in case it's also of help to anyone else:
Although a 'cheapy', my airless gun came with a short (around 5") extension piece which is flexible- when you bend it, it stays pretty much in shape. The actual nozzles have a cone-shaped flute around the end which makes it wider than I'd like, so on one of them (forever to be used for Waxoyl!) I trimmed this unnecessary part off, leaving just the actual nozzle part which is around 20mm diameter. This allows it to get through smaller holes, but more importantly lets me press the nozzle
tight against even
very small screw and bung holes, etc and spray directly inside without unwanted stuff going sideways!
To spray the
front inner wings sections, I got access from the very front by removing the side light assemblies (if you look 'up' after removing the light, you'll also see that the outer wing at this point is single skinned, so spray up there too!), and from the back of the wings via the large gaps between the inner and outer panels you'll see when you open the front doors. Just press the nozzle up against these gaps and fire away! From under the bonnet you can also see some holes which give access to the inner wing sections - go for it!
Bear in mind that, for these particular parts, I diluted the Waxoyl
significantly beyond the recommended amount (they recommend using White Spirits) - I reckoned this would allow it to travel further and in a finer 'mist' which would seep by capillary action into the arch seam joins which was my main target. I believe this worked as the Waxoyl would trickle and 'run' where it landed in a pool whereas normally it wouldn't as it was too thick. I could see that, when I sprayed into these confined spaces, the spray mist would really 'fill' these voids, giving everything - up, down and sideways - a neat coat. Similarly with the sills - I didn't bother removing
every bung, just the end ones and one near the middle; when I pressed the nozzle tight against the holes and sprayed inside, Waxoyl mist would come
out the other holes - pretty reassuring.
You can always add further thinned coats after a couple of days if you also wanted to build up to the usual thickness.
For the
rear inner wings areas, access was gained by removing the very rear oddment trays (one has an ash tray) which are held by one screw each. I bent the nozzle to aim downwards, and fired the spray as far forwards from this point as I could, as well and down and back (this is an excellent access point - you can actually see straight down on to the panel seam that I was trying to target). Then, after removing the rear light assys and easing out the large rubber wire grommet, you can spray the very rear section through here.
Again, because of the thinner, finer spray, it basically covered everything inside the arch!
Oh, and I also sprayed through the drain holes on the front edge of the bonnet, as well as into every hole and gap between the bonnet skin and its additional 'webs' on its underneath - try and get the spray right in to coat the inner - hidden - edge seams of the bonnet. Look at any 'van' over 10 years old (and many cars too!) - you'll almost certainly see rust coming through from behind the front bonnet edge.
Oh, oh, and also up through the door drain holes (it would have been much better to have removed the inner door panels, but past experience has shown me that these can be a bu**er to remove without some clips breaking away from the actual panel (in fact I started on the rear door panel, and this happened to the first one I came across - so I stopped

)) I basically removed everything I could remove to gain access to hollow panels sections! Eg: The front doors have rubber bumpers near the bottom which pull away very easily - this provides a perfect little hole to inject through by pressing the nozzle tight against it. The side door has a good gap around the locking mechanism (Don't forget, Waxoyl ain't your usual underseal - I certainly wouldn't have sprayed any type of thick 'paint'-type sealer in these places!)
On that note, I also sprayed all the visible brake pipes and hoses, steering gaiters, all the gear shift and handbrake cables and linkages, all the suspension bushes, nuts and bolts, etc etc etc! Future maintenance will be
much easier. (There are many comments on this forum about the front anti-roll bar bush brackets having bolts which tend to shear off - they
wouldn't have if protected earlier with Waxoyl!!)
Obviously, you don't allow any to get on to the actual brake discs or pads, but I did spray the backs of the callipers so that the bleed screws and pipe connectors will be protected from rust and easy to remove in the future.