I'm not sure what you mean by 'abandon my efforts', but I hope you can keep the lambs going even if the ewe cannot accept them.
Some ewes reject their lambs but come round when the milk gets through the lambs' systems. Others just don't want anything to do with the lambs at all, ever.
Years ago, we used to have things called lamb adopters which were circular, and held four or five ewes with their heads restrained in a yoke. The ewes all faced each other in the centre of the circle, and the lambs lived in the wedge-shaped space where the ewe's body was. That often helped the lambs to feed without being knocked about by the ewe's head, but some ewes just kicked so much that the lambs still could not feed unmolested.
A halter can be used to restrain a ewe while the lambs feed, if the ewe is tied to the corner of the pen. Some shepherds turn the ewe over onto her haunch, with her back toward their legs, and bring the lambs forward to sook at the up-turned teats.
Whatever the problems, it is essential that young lambs get colostrum, and four-hourly feeds whether they be from their dam or from a tube or bottle.
Lambs which are being artificially fed for an interim period, and which are to be returned to their dam for natural rearing, are best fed through a tube eased gently into their stomach, and the milk allowed to gravitate into them. If lambs which are finding it difficult to feed from their dams are bottle fed, there is a risk that they will lose the desire to sook the ewe, and that will cause more problems.
When trying to get a lamb to sook its dam, the best way is to use one hand, under its bottom jaw, to open its mouth and insert the ewe's teat, while the other hand pushes the lamb forward by pressure on its bottom. Pressure on the top of the lambs head will only result in the lamb pushing upwards, or reversing out, and that can make it difficult to attach it to the teat.