Own design and build sports turbine jet

That's what I thought BB was doing, but to my mind, he is doing it inside out!
You want the perfect finish on the outside of the plug, not the inside!
If you dig back in the files, you will find that I posted how to make a glassfibre fuz - on here - about three or more years ago.
I always used a wood core, split lengthwise, then bolted back together, BEFORE the shape was carved, so it ends up symmetrical. Then the core is split, bolted down onto a flat plank, and the mould made in glass, in two halves.
When THAT has cured, they are eased off the plug, carefully aligned, drilled through the flange, for more bolts, and then you can make the fuz. The two halves can be released, returned to the mould, then the seams taped via the access hatches.
As you say, a lot of work for a one-off, but ideal if you intend to make dozens from the master.
Many years back, I used to work in a glass-fibre manufacturing place, (health and safety hadn't been invented, they'd be shut down, now, but they went bust instead!) and used to 'borrow' their tools for making my own plugs, during the lunch-breaks. I also managed to 'find' some surplus cloth, chopped strand, bandage, resins, and accelerators!
I'd have to buy it, now!

I doubt that there's a Halfords in Cyprus, O.F!
BB, try using more water and less pressure, on the wet and dry. It looks like you are getting 'beads' of residue, which are then scouring the finished surface! Also try using a much finer grit!