hi jeff ,i already have lance,gutter attachment and nozzles. i tried cleaning my sister in laws but found that when i did inside the gutters the mess run down the back and the house . is this a big problem and what do you do to solve it or is there a technique to it .
You will get the black water run down the back of the guttering, but don't let this put you off?
Start at the end furthest from down pipe, let the black water run at the back and don't panic, just continue this way until you reach the down pipe, most of any big stuff will have blown out by the time you reach the end, if not it will have been watered down so much by the pressure that it will flow into the down pipe with no problems.
When you get to the down pipe, stick your Jet into the down pipe and give it a 10-15 seconds blast, listen for the water running down the pipe if you can't see it.
If the guttering has what I call an extra garden growing out of it, you may have to remove this first, this is why I designed my Mk1 gutter cleaner that I posted pictures on.
I spent to long on a Job that had extra Gardens, just by using the lance, it will eventually blast the deep rooted ones out, but its time consuming, and I like to get a Job done with speed and good results.
Once you have cleaned out the guttering and you feel happy with the job, remove the gutter tool, Just the U shaped bit, add your jet to the straight piece (not the pencil jet if you purchased the set of 5 nozzles) the Jet you need first of all, is the black one, the one with the largest hole, fill your detergent bottle up in your pressure washer and begin the application of your detergent, (this takes a few seconds before it comes out.)
Start at one end and apply your detergent to the guttering, facia and soffits as you go along the run, once you reach the opposite end, then change your low pressure jet for one of the high pressure jets of your choice again not the pencil jet.
Begin your cleaning from the point you first applied your detergent, starting on the external section of the guttering, clean all the guttering including the back of it, the black you washed out and that run down the facia's will now begin to be removed, it takes seconds before it runs clear, once you see clear water move on and continue until the run is complete.
It will take you a few houses to get a knack for it, I find that once you have the knack, you will learn to adjust your lance height until your comfortable with it, I found resting the lance on my hip can speed you along in comfort as your hip is taking the weight of the lance and not your arms.
Once the job is complete, its time to tidy up, take a soft sweeping brush with you and clean up any large pieces that may be there, don't bag it up but put it around any plants in the garden as its mainly rotting plant matter and becomes good compost for the plants.
Get your lance and just spray from a distance any other dirt laying around, don't go to close to the ground with your lance or you start to clean dirty concreate etc, just use enough spray to move the dirt you created, and direct it again to a drain or bush area. The whole cleaning job shouldn't take more than 10 minutes, any dirt left in drains can normally be washed away, if its big clumps, again just put it around the roses.
HTH?
hi jeff, doesn't all the crap from in the gutter block the custy's downpipe and sewer runs?
not a pop, just an honest question. 
Hi Dave
If you don't make the effort to remove the extra gardens as I call them before you begin the clean, then I can see there could possibly be a problem, one of which I have never had yet.
I take with me (Just incase) a steel mouse on a reel, if blasting from the top with the lance doesn't work, then I would run my mouse up from the bottom and break it down, then finish with a blast from the top again.
If you do a Job correctly to begin with, this problem won't accrue, there is to much water for the drains to become blocked, as underground drainage is in 4'' pipes.
