Split latch & plaster gibes with what I was taught in Architecture school (and have learned in the 38 years hence).
The lath was split from various local wood to about a 1/4" to 3/8" dimension (8-10 mm). The lath was nailed to the supporting structure. The lathes were abot 1/2" to 3/4" (12-16mm) wide, and spaced about their own width apart.
Plaster was applied over the lath in three coats. There was a thick initial coat which "bit" in an around the lath. After that dried a "brown" coat over that flattened out the surfaceand gave it an even plane. The last coat was the finished coat. This last coat was into what murals were painted. Final thickness was about 1 to 1 1/2" (25-30mm).
Ok, fine, This Old House recap useful, but, more to the point, how do we replicate this in 1/35? Well, 1" is right at 1/32" or 0.7mm in 1/35 (I'm cheating abit and converting from 1/32, or 3/8" = 1'-0" am architectural scale I have a high familiarity with).
For plasterbpard, I've used thin Crescent Board, a product available in the State that is very similar to Bristol board, in being available in both hot and cold pressed face, crescent board also being blue-green on its back. Thus the white face simulates the finish coat of plaster, the green back the mill face of the blue board.. But, what we want is lath & palster.
So, what I think our brother Bish needs is a bit of bristol board with a moderately rough texture (cold pressed is the stationaries term-of-art), or perhaps a water-colour bristol board--the stitioners will eyeball you funny when you mike their stock a bit--but better that than A, not buying any, or B, bringing it back for being 2mm thick.
Simple answer for the lath would be to use a brown felt tip pen to rulle out some fine lines about 1mm apart. Then give that an overspary of, say, light gull grey (dust cakes on the top of the ceiling).
Now, lath an plaster when hit with blunt objects (excavators, skid steer loaders, air dropped ordinance) the plaster will come off in chunks, levaing the lath to break where it will. Similating lath at 1/35 will be vexing. being about 1/64" square--call that .3 tp .25mm. If we all had, say, Pawel's skills, I suppose we'd go get a 1x3 strip of linden or boxwood, and using a spokeshave or plane to split slivers from the length of it, then pressed into milliput rolled to 0.7mm thick :)
The rest of us might use fine foil or chartpak tape in sutible sizes. I happen to have a hoarded stockpile of cigar tube spanish cedar veneer which I'd part out using a couple of xacto blades clamoed together.
Maybe some of that will help (I feel like I'm having a Tanker Builder momnet here)