Normally (at least on this side of the pond) a banjo's peghead is cut with the fretboard face held to the jigsaw or bandsaw table as the contour is cut.
I normally make classic or flamenco guitars and frailing banjos. It sounds as if you have fret wire for an electric guitar. ???
Yeah I was considering cutting the peghead that way, I didn't know it was traditional I just thought it'd look cool. But with my bandsaw I think it would've been a difficult cut. Also usually banjos have funky heads but i'm going for something fairly basic here.
I was very tempted to go for this style of headstock.

It's one of those 'so stupid it's cool' sorts of things. Pompadour banjo. I think i'd only be allowed to play rock n roll with it.
But yeah following a template seems like it'd probably work out better. I'm a little concerned about routing endgrain though. I'll have to take it very slow.
As for the fret wire, I did buy it from a guitar place at about the same width as what my current (cheap) banjo has. But I can't imagine it'd make much of a difference. I imagine you could probably go a bit thinner with the stuff on a banjo, with the lighter strings. But my old banjo's frets are surprisingly worn after not a huge amount of playing, so I didn't want to take any chances.
Anyways I got the thing slotted.

Being the most critical part of the banjo i'd naturally not given it alot of thought and came up with most of this stuff as I went along. I figured i'd use paper templates since they tend to be more accurate than a tape measure. But I wasn't sure how to attach it. Usually i'd use spray adhesive but I don't really want to have to sand it all off, since I was clever enough to get the fingerboard to exactly the final thickness before slotting it. I also didn't want to use the double sided tape since it'd probably gum up the saw blade and tear off while cutting. So I went with putting a few spots of tape to lightly adhere the template, then marking each slot with a chisel.

Was pleased the lines came out so visible. It's stuck to a bit of MDF to keep it lined up properly in the miter box.

Got a sort of junk miter box that the saw butts up against. The cut is lined up by eye, by stooping down and getting the sawblade in line with my eye I could see the reflection on the wood below to line the cut up pretty well. A light backwards stroke with the saw also confirmed if I was on line or not.
Now if this is accurate or not, i'm not sure. There's probably an error in lining up the paper templates (that were in 3 parts for this), there's an error in marking the chisel line, and an error in lining up the sawblade to the mark. It could be a considerable ways off by the end of all that. But I think that, for the first 10 or so frets, being within 1mm of the intended position will probably be fine. I don't think i'd be that far out.

I had a hell of a time separating the MDF from the fretboard. The old carpet tape I had was more like duct tape and didn't stick all that well, but this new stuff is intense. Opened it a bit to begin with using a chisel then slipped this steel ruler in and hammered it down.

Then used it like a knife to get the rest off. I flexed the fingerboard well past what i'd assumed it would've been able to survive, but i'm glad it didnt break.

Before glueing it to the rest of the neck I need to put the 5th string in. I'm not entirely sure if I got the 5th string pip in the right place, and i'm a bit concerned about it really. It doesn't have to be exactly in line with the rest of the strings but hopefully its not so far over it interferes with the 4th string. Here i'm drilling the angled hole for the tube.

A slot was routed out on the other side. Rather than route it deeper I decided to squash the tube a bit in the vise. Checked it still guided the string, then fit it to the recess and fit the recess to the tube. It was then epoxied in. More of the slow stuff, so it'll be a while till it sets.
This epoxy sets very flexible. Usually that'd be a good thing but it might make it harder to trim flush.