The trained eyes at Dixons are not looking for evidence of using period techniques. When building, you have to decide whether or not to build for the judges. If you build in what I'll call "Bivin's style", it's second nature to build them the way the judges like them. Super clean, perfect fit and finish, great clean lines, classic design for whatever school you're working in, nothing funky even considered. Applying "best London" style of working to the longrifle, whether plain or fancy, will work for the judges every time. How you get there (tools and techniques used) or how much your finishing techniques emulate original work doesn't matter.
I have scraped brass but have trouble with chattering sometimes unless I hold the scraper at an angle of 30 degrees or so (crosswise to the direction of scraping, not tilt of the tool from vertical). I switch angles every other stoke, +30 to -30 degrees, etc. For a burnisher I mounted big handles on a piece of gently bent, 5/16" hardened O1 drill rod, so it's about like a drawknife in size. This allows me to really put pressure on the work. A little oil on the work helps when burnishing.