If your coupler is bad, then all the bushings in the linkage need to be replaced.

There are three bushings in the linkage, make sure to replace all three.
1. Coupler bushings
2. Rod bushing
3. Shifter to rod bushing

A kit with all three bushings is less than $20 from our host: https://www.pelicanparts.com/More_Info/PELBUSHKIT1N.htm?pn=PEL-BUSHKIT1N

These bushings wear out, so I would check them every 10-15k miles or so.

There are higher end couplers available that don't wear out, they are most expensive, but they have an even better shift feel and you never have to replace them. Like this one: https://www.pelicanparts.com/More_Info/WVOPSJS2.htm?pn=WVO-PSJ-S2&bc=c&SVSVSI=0581

Here is a good video on replacing all three bushings: https://www.youtube.com/watch?v=jwJrbAPEr68

Here is a good video on adjusting the linkage after you replace the bushings: https://www.youtube.com/watch?v=tEdOeHUYjU0

Errormargin—thanks for posting this, I have adjusted the coupler before (the gearbox was stuck in reverse— I removed the backup switch from the gearbox and levered the pin back in) but this in depth review of the process will be very helpful in determining the state of the various bushings. I am sure other guys will benefit from this as well!

I can downshift into first at speed with no issues (I usually double clutch as advised, but don't have to). Most of the time second is good for most corners etc.

I can shift into first pretty easily while still rolling to a stop.

If I come to a complete stop in a gear other than first, sometimes first requires double clutching or shifting into a different gear to enter. For this reason I try to shift into first while sill rolling slowly to a stop. Then I can move to neutral at the stop, and first is easy to get into when it's time to move.

Being in neutral rather than first with the clutch in is wise as it saves the throw out bearing wear IIRC.

My 84 Targa also has that problem. I tried all the same tricks as you, but the best solution I found was to just come to a stop and leave it in neutral with the clutch out as normal. When I wanted to go, I'd press the clutch in and shift into 2nd and, while keeping the clutch in, then shift straight up into first. It was easy to do and worked like a charm.

May try this one, as long as I get it into first as it rolling down to 5 mph and then to neutral, first is always easy (until it's not). I need to remember this method too in case I don't get it into first while rolling slow.

Thanks

Ditto