One of the reasons I went with a mottled camouflage on my tropical Spitfire was the trouble I had figuring out how to resize the painting guide in the instructions. I fiddled around with the scan, but when I printed it out it was nowhere close to the size of the model. After a second attempt, I was not willing to spend more money on ink. Is there a quick way to do it, or is it just guesswork combined with trial and error?

It's easier with a photocopy machine.
You measure f.ex. the wngspan of the model and that of the instructions, and a quick calculation will give you the reduction (or enlargement) needed.

Quote from: The Rat on February 26, 2024, 01:50:13 PMOne of the reasons I went with a mottled camouflage on my tropical Spitfire was the trouble I had figuring out how to resize the painting guide in the instructions. I fiddled around with the scan, but when I printed it out it was nowhere close to the size of the model. After a second attempt, I was not willing to spend more money on ink. Is there a quick way to do it, or is it just guesswork combined with trial and error?

Set working units to inches and use the artboard rulers of the program.

Instructions on paper are flat. A model, especially an aircraft fuselage often isn't. That might cause issues making it work.

There's calculators online which tell ya exactly how to resize ya measurements from plans to the model and will give you the percentage on which to enlarge the printout by .
If you have a photocopier with a scanner aswell it's much easier.
In the back of both of Shepherd Paines model books he has plans for models he scratch built and luckily he givd you the scale and percentage in which enlarge em to 35th scale.
One was the Israeli M51 Sherman and the other the M26 Dragon Wagon tank transporter..thankfully Tamiya sorted that out 
I did this when I built the M51 Sherman from Sheps plans.