HI Otto, sorry for late reply as we have been traveling interstate the past week or so.
The corrugated walls are a plastic product from the UK called Slaters. I have used it for years in N, On30 and now of course my HOn3 layout.
I firstly lightly scribe the lines for the dimensions I want for the corrugated iron sheets once laid (I use a #11 medical Scalpel ). Then spray the building with Tamiya Flat Gull Grey or sometimes even just Tamiya Light Grey Surface Primer. Once dry spray with Dull cote. Then I use Tamiya Panel Line Brown paint to carefully apply this to each scribed line to highlight the seams. The rust on the roof sheets is done by laying down a strip of Tamiya masking tape on the lowest edge of each sheet. Then I dry brush from the bottom up on each sheet using Tamiya Red Brown lightly and once dry a similar process using Tamiya Hull Red.
Seems to come out okay.
You might gather I like Tamiya paint. Yep, I have used it for more than 30 years and it has never let me down.
Rod.
