Not exactly sure how this will be taken on the forum, but we've done it for the last 5 years & have yet to have a cow reject a transplant calf-- I even transplanted a 6 week old calf onto a cow that just lost her 3 week old one..
After a cow has lost its calf we'll hang the calf up & skin it, just like a deer. We remove the hide from the top of the shoulders, down to the calf's forearm, to the belly, stifle & we make sure to keep the tail (still has the cows scent on it). Catch the transplant calf & tie the hide on with a piece of twine, just like a little jacket. First time we put the pair together, I put the cow in the head catch with some grain in front of her, just so shes quiet & content & we can make sure the calf knows what to do... I've seen some 'not-so-bright- ones we've had to work with lol. After that, we usually turn the cow back out to a bigger pen with feed & water until the next time its time for the calf to nurse (we usually go 7am/ 1pm-ish/ 7pm)-- Key to this, make sure the calf is in a pen right next to the cow where she can still see it. The next time we get the pair together, it's usually just in a smaller pen, put a pan of feed down for the cow & calf 'should' do his job. When he's done, put them back in their designated pens. I'd say, on average it takes two days tops for them to pair up, granted each scenario is different. After you're 100% certain they are a pair, cut the twine off the hide, but before you throw it away, watch the 'pair' carefully, just to double check that is HER calf. Once you're certain, there's no need to pen them separate.
Hope this helps, and sure hope I didn't offend anybody
-Sam