I did the tuning on my 2 meter helical resonator using an SWR bridge and less than 5 watt transmitter. In practice with only two sections, adjusting the two piston trimmers which are not shown in the photograph is easy enough with just a receiver and RF attenuator.
What was the passband and stop band ripple like? How well did it match across the passband?
In addition, you already have a lot of relevent skills and experience to built such a device. I am pretty sure the OP doesn't, and that was what I was trying to convey. I also doubt the OP has a 5W transmitter or SWR meter. That method is exactly the method I've used in the past, but when you take a filter you've tuned that way and put it on a VNA you realise it's not quite as good as you thought!
When I designed it, the only information I was missing was how large to make the coupling window so I made it 1/3rd the width and height which as it ends up made it massively overcoupled but this had some advantages. Loss in the center of the band was like 0.05dB, there was no measurable ripple, and it covered most of the 4 MHz wide 2 meter band. It was perfect for removing pager interference.
I never had access to a VNA to test it or I would have lowered the coupling. I did come up with a design for a variable coupling window but this one worked so well that I never proceeded with it.
This was actually the 2nd one I designed and built. The first helical resonator was not nearly as well constructed and used film trimmers which lowered the Q significantly preventing operation at even 5 watts because they would break down. After that I found someone selling piston trimmers at the ham radio swap meet which made all of the difference.
The design process for both was interesting. I started with the fixed size of the wire for the helical elements and worked out the dimensions going backwards. The center frequencies with the trimmers were right on. The final product was definitely not an optimal design but it was and still is way more than needed to protect a receiver from out of band overload and the extremely low loss has advantages.
Incidentally, this project was also how I discovered that RF coupling into a gas discharge bulb is incredibly efficient. A neon bulb inserted into the helix with 1/2 watt is way too bright to look at. If I ever build a gas laser, this is how I will do the excitation.