I probably did it all wrong but it worked for me so I took on views but carried on doing it my way. The only ones in my Mothercare were Avent ones but they're probably all the same. I just put them on before a feed and let him feed away on them - the nipples sort of grow to the size of the shield, swell out a bit and are really sensitive after a feed but it's ok they go back down. I think officially you're meant to let them suck for a bit to 'pull' the nipple out a bit, then take them off and let them feed straight on the nipple, but it was too sensitive so I left them on and it was fine. That was the only way I fed him, we didn't do it 'normally' without them but I didn't care as it worked fine for us and I didn't feel any need to do it any other way... lasted 7 months (our choice to stop, not lack of supply or anything) and we could have gone on longer just fine so don't let people tell you it naffs up your supply - maybe they do but we managed just fine that's for sure.
Re: sterilising, I washed them and cleaned them out with a teat brush, and sterilised as per other bottles and breast pump. Then to keep them ok for the next feed I got one of those tiny little storage tubs with clip on lids (or a weaning bowl and lid, anything small and lidded really) and kept them in there. Also handy for taking out in public cos you can just keep them in a tiny pot.
Anything else just lemme know but my OH still claims it's the best £5 he ever spent lol
Worth a try if nothing else x