I spent the morning down on lake 6 at the woolpack with my marker rod and Smartcast echo sounder today and it was well worth the effort. My method is straightforward and made much quicker using the Smartcast. I use my old Hummingbird RF15 which works with the 'Lucky Sensor' on channel B. The sensor is bright yellow and shaped like a rubber duck! You cast this out on the end of your line and read out the depths and contours on the the Smartcast's four inch screen. To get a better signal I have my smartcast receiver mounted on an extendable bankstick about 5-6 feet off the ground.
First cast is made straight out from the swim and the depths noted in my notepad as the sensor is pulled back in. Then I gradually fan out the casts to the left pulling it back, again noting all the depths and then repeat it all for the right hand side.
Once this is done I use the information I have gathered in my notepad and start casting my marker rod over the same areas. This is for two reasons, one I want to check the depths are right and two, I want to feel the lead on the bottom to gauge what sort of substrate it's in and then to visibly mark it by letting the float rise. So any clay, gravel weed or silt can also be marked down in the notepad.
I do this in each swim noting down the depths etc on a separate page for each and then, when I get home I put it all together on an A4 sheet.
This gives me the basic map which I then go on to refine over the rest of the season each time I fish.