Both of my road bikes with under-the-bracket cable routing had Teflon guides.

Since my 1959 Capo was designed for a front derailleur with an integral cable stop, I had to improvise when I installed a newer unit to replace the worn-out Gran Sport (which looked just like a Valentino, and similar to a Simplex, with a pushrod and a square box behind the seat tube). I ran a length of Campagnolo stainless cable housing from the downtube-mounted stop under the bottom bracket, and just let it terminate vertically in mid-air. Works like a champ.