For our branchline, I recently bought some of the subject kits. These can be obtained from Holt Models (http://www.holtmodelrailways.com/search.php?search=mikes). I thought I'd try to provide some insight in the construction of these since I think most of us are used to building plastic kits.
The kits are primarily in cast white metal. The first thing to do when dealing with white metal is to wash the parts with soap and water. I happened to use Windex (window cleaner). Once dry examine the parts and remove flash by sanding or scraping the edge of a modelling knife along the seam. Look at all the holes where parts will have to pass through. Dry fit and use a reamer to to open the diameters until you get a snug fit. Its a good idea to give the mating surfaces a rub with a fiberglass pen
There is some brass chain in the kits. I used Carrs chemical blackening fluid to darken these. Painting tends to clog the links.
Yard Crane (MM37):
Try to work out where everything goes before assembly. For this kit, it is certainly not obvious. Even the photo in the link seems to me to be incorrect. Once I got everything sorted assembly was fairly straightforward. I used medium viscosity cyano adhesive. The only issue I had was getting the crane to swivel. It took a few minutes of sanding the spindle before the crane swung freely.
Note the position of the small gear wheel and brake. It took me a bit of thought to decide to put these where you see them. I couldn't find a picture of this specific crane. My logic said that the operator would want to have the crank and brake close together so, in my configuration the crank can be turned by the right hand and brake operated with the left - this seems right.
I made a plastic card base painted with aged concrete.
I always like to prime my models and when dealing with metals, I believe this to be most important. I use car primer, grey for the crane. When dry, having no idea of the prototype colour, I used grimy black for the frame and gunmetal for the gearwheels. Once that was dry I weathered the model. Everyone has their own method but mine is fairly simple - I simply airbrushed a light coat of earth followed by a light coat of black. I then drybrushed some rusty powder here and there.
Water Crane, Platform (MM6) & Floor Mounted (MM161):
These are very straightforward and assembly is pretty obvious. On examination, my first thought was that the guy wire supports (cast in white metal) are too fragile (in fact, if memory serves, at least one had already broken off). I decided to replace the guy wire supports with 0.032" brass wire. I snipped off the supports, sanded smooth and drilled. It's a good idea for things like this to start with a small hole and work up. You have a better chance of centering the hole. I began with a 0.020" drill (dip the drill in oil, this will improve the cutting and prevent jamming) and when deep enough switched to a 0.032" bit. Wire was glued in and cut to length. I also drilled 0.020" for the guy wire at the other end of the crane. Finally I replaced the cast hook on the drain with a wire version. I also decided to replace the chain attachment with 0.020" wire. Again medium viscosity cyano is the adhesive.
I constructed a two piece base in plastic card and strip. I wanted to be able to plant the cranes in a layout mounted base for exhibition.
Again, primed with grey. After that, since the top coat is very light, I sprayed again with Testors Flat White. THis time I was able to find a couple of pictures of GWR water cranes. I used D&RGW Cream for the body colour (I never seem to have the actual railway colours) and Humbrol Matt Sand. I picked out details in black. Weathered with earth and black and brushed with a light dusting of black and rust powder here and there.
I am very pleased with how these turned out. A modicum of care (as with all kits) will result in an excellent result. Remember that we should be building a model of something using the kit as an aid. Building a kit is something else again. I am never shy to discard parts I don't like or change something.