Fortunately my rattlers have never had a problem shed. Now that I say that the next one will retain the eyecaps or something.
However, one thing I often do with other snakes is similar to the damp towel trick. I use long fibered sphagnum moss. I dampen it well and put the snake in the tub, then sit the tub on a heater to create a 100% humidity environment. The humidity along with the sphagnum being something to crawl through, usually gets the shed off, or else loosens it to the point is comes off very easily. I find that this works much better than soaking in standing water and doesn't carry the potential of drowning etc.
Sounds to me like you need to invest in a set of tubes possibly as well. I bought a set years ago and had never used them until this winter. But having them ended up saving the life of one of my females this season.