I've done this and think its fantastic! We are outside all the time with animals and usually come in with very dirty clothes at the end of the day. Not to mention our four year old !
The ingredients last for ages so you're not continuously shopping for them.
1/2 bar of sunlight soap - grated
1.5 litres water
1/2 cup of washing soda crystals
4 litres hot water
Place grated soap in saucepan with 1st quantity of water. Heat until soap melted.
Add washing soda and borax.
Stir for a few minutes until soap thickens and remove from heat.
Add soap mixture and mix well.
Pour into 2 or 4 litre milk bottles or other bottles you may have, using a funnel or just keep in the bucket.
It will thicken after 24 hours. It gets very gluggy - but easy to squeeze out.
I also add a few drops of essential lavender or eucalyptus oil for a slight scent. (optional)
Have a go - it's easy to do, easy on the pocket, and easy on the land !! :-)