I too found it nearly impossible to swage .40-65 brass from .45-70 brass with a standard reloading press. Rather than resort to putting a cheater bar on the handle for more leverage (which should work if the press and its linkage is up to the task - not many are - and the press and its bench are well and truly anchored), I instead utilize a 5-ton arbor press. Cases go into the die like butter (and are removed via a push rod in the same press). I can envision a rig using a hydraulic jack to accomplish the same thing.

Use Imperial sizing wax which Jack also uses and do multiple passes as Jack suggests.

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It is much more effective for squeezing down cases than many of the traditional case lubes most people use.
However you can not just press/size them with one pass.
Push down until it gets a bit tight.
Relube the case and take another pass.
May take three passes to fully squeeze extra wide case webs.

Only a slight film of this wax is required on the case down to the case head.

When you anneal only do the necks.
Do not anneal the web or lower portion of the case.

Thanks for the swift replies. I think a large part of my problem is that my loading press ( Lee.) is not mounted onto a strong workbench allowing quite a bit of flexing.
I will see if I can source some of the Imperial sizing die wax and try again using someone elses press that may be more firmly mounted than mine. 
Thanks again.
Mike.

I made up a bunch of .40-65 brass from .45-70 decades ago using my Rock Chucker press and Imperial sizing wax. I could do it in two steps to full length size the cases, but three steps did it without as much effort from my right arm.

If you have the seating die, and it is the full case type, run it through that first. The few thousands difference in diameter makes a huge difference.

Thanks again for all the advice, I have a friend coming over this afternoon to pick. up some of the cases and give them. a try in his press using Imperial wax, hopefully this will work out OK.
Cheers
Mike.

Mike, if you can't find Imperial wax I find that lanolin grease works just as well. I've used this to form .33 WCF & .38/56 WCF from .45/70 brass.
Pete S (Spud)