I used Lansinoh lanolin to lanolize the wool soaker... in fact as long as it's 100% pure lanolin any brand will do.
1) Firstly, get an empty container as we will need to melt the lanolin in it. Remember to use hot water for the melting purpose.
2) Next, a pea-sized of lanolin will be enough for a soaker. If you have wool longies I suppose you might need to use more lanolin.
3) Add hot water ( I don't use boiling hot but it works too) and you will notice the lanolin starts to melt. Cover the container and shake well. Preferably get a see through container with lid/cover so that you can shake it without pouring out and see for yourself whether it's already all melt.
5) Rinse the soaker and prepare a big container or washing pail that is big enough to lay the soaker in it. I think laying the wool soaker horizontal or vertical is not a problem. Please correct me if this has differences and purpose.
7) Pour the lanolin that was prepared earlier into the water and stir to mix. Let it set for at least 30 minutes or overnight. I prefer later but frankly speaking they don't differ in any way.