You do speed up with xperience. i'm at them all the time, and, believe it or not, i can sometimes strip a 4-500kW boiler down faster than a 21kW one.
Couple of tips.
Get yourself a pair of welding gauntlets, custards always forget to turn the boiler off before you arrive, these will buy you a bit of time and you can handle the baffles a bit sooner.
Carry a sheet of Cera board. You'll quite often need to make new seals where the old one's perish or become water damaged if the flue's not been weathersealed properly. (that's a nice little earner off the back of a service)
Get some copper ease grease from halfords. a dab on the threads makes dismantling next year a doddle.
Carry plastic polypockets and a preprinted sheet giving your contact details, and somewhere where you can record details of work done (full service, replaced 0.60/60s nozzle and oil line, cleaned filter etc) and date next service due. You can also leave a print out of your fga results in it. Leave on site. Custards like looking at stuff like that.
Use the web, find as many MI's as you can.
And use this forum!