aircraft panel lines - help!

I think you can also get ponce wheels anywhere they sell sewing supplies.

in 1/72nd scale I think you can safely lose most of the rivets, or at least rub them down until you can only just see them on the bare plastic. Go & look at the Shack from around 50 feet away, where did those rivets go to? all you'll see is paint & shadows. This subject has been discussed before on the forum, mostly it came down to personal taste & how you want your model to look.
If you want to put rivets on the replacement parts, find a good jeweller & ask about a ponce wheel. Imagine a cog from your watch on a stick, the cog can rotate as you wheel it across a surface. As it does so it makes 'dimples'. That's a ponce wheel.
I've never used one but I've seen the results from one & it looks good.
Remember that the Shack kit is very old and the surface is overdetailed as were most kits of that era. Having said that, a common RAF name for the Shack was;
3 million rivets flying in formation!

As for panel lines I always toyed with the idea of covering the model in bare metal foil (aluminum color) and overlapping the sheets just like the actual aluminum panel lap joints. This should provide a nice scale panel line. And you can even chip the paint off exposing the metal underneath!

thanks

it's going to need some practice before I start on the Shack. the thought of all those rivets (must be thousands to do) is giving me a headache

tiny blobs of dimensional fabric paint work well for my 1/72-76 AFVs. Look out in your local craft shop or embroidery kind of shop. Get a colour that will stand out from the plastic! Use a sharp cocktail stick to place the blobs onto the surface of your model. It takes a bit of practice to get a line of regularly-sized 'rivets', but it's the easier way I have ever found to replicate them. Once you are happy with your work, seal the rivets with a light coat of Jonhson's Klear (from your local Tesco).