I recently got a huge lot of bars of soap at Gabriel Brothers, 6 bars for 1.49. I ended up buying about $60 worth because the soap is hypoallergenic, not too strong a fragrance and it grates very well and breaks down to a very fine powder and is excellent for the dry laundry soap!
It grates very easy and I grated 24 bars of it into a 3 gallon bucket, took my hands and squished it all into a very fine powder and then added my borax, washing soda and oxyclean.
I made a 3 gallon bucket full and I put some (about a quart or so) into an old tin I had and use a small scooper, about the size you use for coffee. I do use 3 scoops because I wash big loads and want to make sure they're clean.
It dissolves very well, I will not go back to using the liquid soap because it's a bit of a pain when I run out and have to make a new batch in a rush and the bucket is heavy and hurts my back when I have to lug it around and pour from the 5 gallon to the smaller container.
I love how fresh the dry powder smells and that it does a great job at cleansing.
I was a die hard liquid laundry soaper, I have now converted to the dry method and I love it. There really is a lot more freedom and less bulk!