Re: IR Calculator and r/s/r bp
The first rinse is important as it gets the surface iron off the bp.
If you can swing it you could do this at home and save yourself some hassle. A super easy way is to get some of those nylon paint strainer bags and put your bp in it for rinsing. I use those lace lock thingies and some stretchy cord to "tie" the bags shut. I also have one of those little metal mesh thingies to cover the drain in case of bag malfunction. Though someone good with knots could use string? A miller's knot perhaps?
Rinse with running water (those cool shower hose things popular in kitchen sinks are great for this). You can then fill the sink, soak, empty sink,rinse the bp again and set in a colander to drip for a bit. Put the bag in a plastic bag to take to the barn.
I do this daily with 50 oz (dry weight) of bp for my mare.
Oh and since we're on the subject of rinsing bp, some people ask about shreds vs. pellets. I remember Dr. K suggesting shreds over pellets because there is more surface available with shreds which means more iron gets rinsed off.