Hand thread taps for stainless steel

I’m finding myself doing quite a lot of thread cutting in stainless steel lately, particularly 304 and 316, often these are moderately deep threads ~ 25 mm or so and at M12 it is becoming a bit of a chore. I’m using a decent tap wench and cutting oil with carbon steel taps (taper, second cut and finishing/plug) but I was wondering if anybody has any experience or knowledge of any ways to make this a bit easier eg by a different tap material or coating.

I’m not doing enough volume to justify any major investment in tooling as this is all prototype work but it’s that difficult area of a dozen or so at a time.

Also it is specifically stainless which is the problem and these are stressed welded components so free machining stainless isn’t really an option (as far as I know) and I do appreciate that this is a bit of a ‘how do I have my cake and eat it’ type question.

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The main issue is the taps getting progressively tighter, I haven’t broken any yet but they often feel like they are getting to the point where they might. I generally start the taps off in a lathe (not under power) with a sliding chuck in the tail-stock so I’m fairly confident that they are going in pretty square.