Because the stringers on these kits are 3/32" sq. I used 3/32" thick sheet balsa for the infil.
These kits are slightly easier to infil because the formers are not notched. The infil runs can be 4-6" long and span several formers if need be. With a kit that has notched formers, the infil pieces have to fit between the stringers and formers. It
adds quite a bit of time to the process but is well worth the effort. You also learn how to streamline the process after a while and it isn't so daunting.
Because the stringers on most guillow kits are 1/16" sq. I typically use 1/16" sheet stock for infil.
Once you have the major components completely infilled you begin the process of sanding, puttying, and sealing.
When all of that is completed I detail the cockpit and landing gear, cut out and detail the gear bays and depending on how I wasnt to display it - the flaps, wing slats and air brakes are cut out and positioned.
I agree that a well prepped but unpainted infilled fuselage looks good.
The idea is to get all surfaces as smooth and glossy as possible before painting. I use a small block down to 320 grit - then polish the wood with a folded piece of ultra fine 1500 grit. The shine you get exposes any defects in the wood surface that might telegragh through the painted finish.