Nice looking Continental, Fred, well done finish, really sharp looking.
In high school in the late 1960's, early 1970's, I read from either Walt Musciano's or Keith Laumer's book about designing and building flying models, on how to rule lines using either thinned dope or India ink and a ruling pen.
First airplane I ruled control surfaces on was an 18" hollow log Scientific Cessna 180, then a rubber powered Guillow 18" Fokker DVIII lined in India ink after I sealed the entire plane's tissue covering with thinned sprayed clear dope. Those ruling pens were tricky, but I managed to do a decent job.
On the CL jobs I'd protect the lines with brushed Pactra, Testors or SIG fuel proofer. After, at times I've used drafting chart tape, some 1/16" wide, 1/32" wide. Then seal the tape with fuel proofer. Been a while since I did, don't know if still available. Lately haven't been big on details. Lined or no lined, they crash the same.