I'll be happy to - Finishing starts at the beginning. What I mean by this is that selection of the stock wood is of prime importance to me. I have built enough guns that I recognize certain qualities or lack thereof in a piece of wood, qualities that will have direct bearing on the final appearance of the rifle. Allowing for some variables , going into a project I always have a feel for what the finished appearance of the gun ought to be. I won't just grab any piece of wood and start flailing, there is going to be a piece somewhere that talks to me and I won't start on a project without it. For many projects there is a range of what I'll accept, but for some it is very specific.
The piece I needed for the rifle you asked about didn't need to be the hardest piece - not soft by any means, but I was looking more for a piece was perhaps denser than hard with an undulating and fairly tight figure, strong in the right areas.. this much of the description covers the working properties. The stock was to be shaped mostly with planes and scrapers. I wanted a very worn appearance to the stock with parts of the figure appearing dropped out or shrunken, and I knew that using those tools with a slightly coarser technique would add to the desired effect. Also wood with these qualities will often take the stain and finish quite differently than other types, also adding to the total effect.
Other properties that I needed were perhaps more readily apparent and immediately visual. I needed a certain look to the grain, and the placement, size and intensity of the figure were important too. I wanted to have strongest figure in the butt end up through the wrist, with the curl roughly the same width as the elements in the wrist inlay. The higher intensity of the figure there would give not just a good color contrast within the stock, but the ripples in the finished wood there would also have a texture that matched the way the pewter would stand slightly proud of the wrist. From there I wanted the figure to fade and return in intensity out through the forend, which to me gives some visual interest.
To finish the stock, I selectively fine scraped certain areas then stained with a 3 to 1 nitric acid stain pretty well depleted with wrought iron filings, then lightly sanded the stock, more so in higher wear areas. From there I applied boiled linseed oil cut with good turpentine. After letting this dry for a few days I started to apply an oil based varnish. The first coat of oil and spirits of turpentine and the first couple coats of varnish I tinted by grinding in dry pigments.
A lot of these things are very subtle individually and I rely on a combined layering to get to the final outcome. It is suprising sometimes how dramatic an effect can be achieved by making small changes - and sometimes dramatic is not what you are after. For that reason it is very important to use cutoff pieces of your stock wood to test your techniques, and also important to go through your whole process before committing it to the rifle.
When working with steel or wrought iron, your choices of materials are much more limited than with stock woods, but there are still many working and finishing properties to be considered, so I approach the iron work much in the same way as I do the stock work. For example, the guard and triggers on the rifle you are asking about were made to look as if they had been saved from an earlier Piedmont gun and reused on this rifle. The material they were made of was different than what was used on the rest of the gun, and they were also finished differently. I wanted them to look as if they'd had a previous life before they found there way onto this rifle.
The iron work was pitted with aqua regia, a couple uneven coats and long times in the damp box. After that I scrubbed it mostly bare, leaving it a bit scaley wherever I thought it needed it, then started to build the surface color with a weaker acid solution. While this is going on I rub some of the high spots back, let them rust again, rub back again etc. You have to know when to stop, in the past I have gone too far and you end up erasing alot of detail you worked hard to get.
Lastly I neutralize a metal finish like this by washing in a strong ammonia / soapy water bath then heat and flood with oil, wipe it down when it's cool. For this one I also finished it off with Rennaisance wax after a few days.
Like with the stock finish process I described, I do not use this metal finishing method on every gun I make. Each one has it's individual set of needs depending on what that gun needs to be. The way I often approach it is to look at the idea I have, understand what I am going to try to do with it, and then figure out what tools I am going to need to bring it to life.
I never used to think about my work in these terms, really never gave it much thought at all. Teaching gun building classes has forced me to think about what I do and why.
How much time does this kind of thing take? I don't keep track. I don't even look at the calendar much any more. I work on guns six or seven days a week, I guess if I start one and it's hot outside but it's snowing when I finish it, or if we hear from more than five bill collectors in a week it means I need to work faster.