I've just had to do exactly this with two of a neighbour's lambs. I kept them in a lambing pen in an enclosed area with other sheep and lambs around them while they got used to me and the bottle. This minimised the stress as it takes only a second or two to catch each of them each time - no chasing about.
At each feed - which I did 3 times a day - I caught each lamb, put its bottom into a corner of the pen, stood astride it restraining it between my calves, offered the bottle - put it in the lamb's mouth and did the usual things to encourage it to drink. I didn't worry about how much it took, if any, as each was eating plenty of cake and hay, and drinking water.
The first lamb took to it within 24 hours, and was coming to me for the bottle by the third day. The second did start to drink a little by the third day but it took nearly a week before it seemed to actually want the bottle, and it had to be caught for another couple of days after that. Now of course they are just like any pet lamb and would follow me to John O'Groats
I think the key things are to minimise stress - so the small pen where it's very easy to catch each lamb, don't be stressed yourself and don't make it a fight. Be relaxed about whether they take the milk or not. At 4 weeks if they're eating cake and hay, they will survive without milk if they have to, they'll just do a whole lot better if they get another 3-4 weeks on milk. So no need to be stressed
. And if you can have them in their small pen with other bottle-fed lambs around them that would be even better, so they can see the other lambs getting fed by you and not being frightened of you.
Leaving a teaty bucket up with some milk in for them to investigate is also a good idea and may well work.