Just my opinion: if you want to do something like this, then get it done right, by someone for whom it is second nature, or else learn yourself how to do it before messing up a nice bike. The Johnny Berry frame shown by Doug Fattic above, and (though harder to see clearly) the two Ellis Briggs frames have a characteristic that, to me, typifies this type of work and gives it a particular charm: the ends of the lines cross a bit, and each line appears to be slightly thicker at/near its termination. See also any Jack Taylor frame, even though they appear to have used a different (roller wheel) application method. I think that the reason for this is the hand speed is slowing. Doug Fattic might confirm or rebut -- I've never seen such work in execution except for the Taylor brothers video referenced above.
Go to about 11:30 for the box-lining portion (the commentary by Jack, the Taylor brother doing it, is very interesting in this context), but the whole thing is a lot of fun.
When we used to do architectural drawings manually, whether using ink and technical pens on board or film, or using plastic or graphite lead on film or vellum respectively, there was a technique for doing this called "snap and punch" wherein one would emphasize the ends of lines by applying greater pressure with lead or a slower pace at ends with ink. It did pretty much the same thing, and I continue to draw lines (manually) this way instinctively.
From a DIY perspective, I've done decent-looking lug lining (completely different) using Decocolor paint pens (fine or extra fine), and have contemplated doing the longitudinal ones with an edge-relieved straightedge in some sort of jig fastened to each tube; but I haven't figured out a good way to do the cross-lines in a way I wouldn't muck up.
As might be obvious, I feel that the approaches done with some sort of masking or with tape result in something lacking: lines not just the right width, the masking "peel-up" along the lines being obvious.
And, why isn't Rudi Mayr (
rhm) at this party. I think he's pretty much the DIY graphics look-to, and have really, really enjoyed his various posts on this topic.