indigo - it's quite similar to the whole retained reflex thing in the going back to the start and re-learning/ doing everything idea (so that you work through the bits you might have 'missed'.) so starting from mark-marking and progressing through different activities all moving towards handwriting. it's not an assessment tool, but ot's use it a lot as a programme to help with the fine motor issues/ handwriting stuff. (the partner - is it lois addy? is actually an ot and helped devise it in conjunction with the teodorescu chap)
as others have suggested, it's a series of exercises that are supposed to be done in order at frequent intervals, so it isn't something that you can dip in and out of at home (unless you are doing so in conjunction with school or whoever is running the programme). it takes about a year, usually, to work through the entire programme, but it is faster if you do more activities at a time/ less interval between, obviously.
if you are going to buy one for info, i'd suggest ordering a new one through the dyspraxia foundation. i found out the hard way that amazon rarely stock it, and all the marketplace ones are second hand and either incomplete or already completed.
i actually quite like it as a programme. it seems very slow, but like retained reflex therapy, it takes a while to get used to the fact that you have to re-do very basic movements etc, and in order of development, before you get to the bits that are problematic. it's human nature to want to say 'why are we working on crawling when i want him to be able to walk and run?!'
there is an accompanying parent handbook thingy that explains the programme, if you don't get given one and they are going to use it, then give me a shout and i might be able to find ours (have a whole stack of fine motor books somewhere, so can't promise - i can never seem to find the one i'm looking for)
op, if the ep thinks that your ds has fine motor difficulties generally, then an an ot referral would actually be more beneficial than just recommending a programme (ep's aren't occupational therapists, so wouldn't usually be speaking from a position of authority on such matters - more of a braod brush approach). after a more thorough assessment of actual difficulties, the ot would be able to put a more tailored support programme in place. it may not just be writing programme that would be beneficial per se, but an ot would look at seating (some children use wedges or wobble cushions etc) or even a writing slope, or a whole variety of different pencil grips etc. there are also lots of exercises (not writing exercises, more of the basic strengthening variety) that might be helpful.
but write from the start is a fairly usual package for handwriting difficulties.