Tricking older cameras: Flash Exposure Compensation

I think I need more coffee as I am having difficulty reasoning this one out myself.

My older cameras have (obviously) an ISO setting and also an Exposure Value (EV) setting. Before anyone jumps to any conclusions, I know that setting ISO 400 and EV +1 is basically the same as setting ISO 200 and EV +0. This is not a question about that.

So, newer cameras have a separate Flash Exposure Compensation (FEC) setting (that affects the strength of TTL flash) independent of the EV setting (that affects the entire frame).

My question:
Is there any way to "trick" the camera and/or flash with settings on the camera and/or flash to simulate the FEC function. I typically like between -1 and -2 for FEC as it is more subtle (using as on-camera fill-flash pointed straight forward when outside, or bounced if inside).

I know completely manual flash power settings are an option but I am trying to figure out if there is a way to make this work with the cameras' TTL capabilities.

Thanks!

In the unlikely event that this matters, the camera/flash combos are as follows:
Pentax 645 (non-N) and AF280T and AF500FTZ
Nikon F3HP and SB-15 and SB-16
Nikon F5 and SB-28

I use an SB-28. I use the flash in manual and adjust the output when I want to do that. It is pretty easy with the distance chart on the back of the flash.

A-ha! I knew I had read it somewhere! In the excellent book The Nikon Flash Guide by Thom Hogan!

I will paraphrase:
Set camera to manual mode, meter scene, set speed and aperture desired, then set -1 EV (or whatever desired), turn on Speedlight and set for TTL mode, ignore warnings of under or over exposure (as long as within capability of flash power, should be ok).

Also forgot that the SB-28 (and maybe some of the others) have the FEC built into the flash itself (as opposed to setting via the camera body like I am used to doing on my D7100).

Knew I just needed some more coffee!

On older camera for example the Nikon F3, setting the EC affects the flash. To also control ambient exposure you would put the camera on manual. The TTL flash still works in auto and takes into effect of the EC setting.