Keith, if they are shot at a modest ISO's (say ISO 800 downwards) I just tend to use Lightrooms own NR with a lot of masking applied. If shoot slightly higher (ISO1,600 upwards) then I tend to develop in LR, then turn off all sharpening and noise reduction in LR, then select "Edit in Photoshop", and when in PS, using my Topaz Labs "Denoise 5" plug-in for NR and then run it though the Topaz Labs "InFocus" plug-in before saving and sending back to LR. Seems to work for me ?
Whilst the 300mm F4 is an expensive lens, the beauty for me is that extra stop of light. If I used my Nikon D500 for example, which has at least 1 stop better high ISO capabilities than my Olympus, I would be using my Tamron 150-600 lens (or if I owned one the Nikon 200-500 lens), and both these lenses would be F5.6/6.3 at the long end and so this tends to mitigate the ISO difference. Then I have a much smaller / lighter package with superb image stabilization and great image quality. Obviously I still have to be realistic with my ISO's so only shoot up to around ISO 3200-4000 max on the Olympus, whereas on the D500 I can go up to ISO12,800 with careful exposure and processing so it sort of depends on what the conditions will be like on the day. Also, whilst I have the 1.4x teleconverter (to give me 840mm effective), that reduces my aperture back to F5.6 so tend to only use that when the light conditions are good (i.e. birds in the open and not in shade / undergrowth).
TBH, it's one of the reasons I sold my Fuji kit, as the Olympus system does me for 80% of my shooting and when the conditions get tricky I have my D500 and long lenses (as well as a few fast primes) and for me at least, the Fuji (whilst a very nice system), did really add anything new for me image quality wise, that I couldn't get with the other two.