You may be using this already but if you buy kiln dried sand it is totally dry and as long as it doesn't get damp it remains "fluid" for a long time and it's easy to recycle. It used to be about £5 a bag so it's quite cheap, I always keep a bag in hand for the odd job that is a bit stubborn. Knowing how messy it is to blast things in the open air I think you did a good job coming up with the idea good for the garden though!
