I put the can in a large stockpot and heat to make it runnier, then pour in the FV. Use some of the hot water to wash the can, and pour that in the FV. Then add the rest of the hot water from the stockpot. Give it a good stir to dissolve the LME, and then add the sugar and do the same. Then top up to desired volume with cold water from a height, stirring the whole time. Ends up well oxygenated and roughly the right temperature; I never had a problem with my kit brews.
I generally have the yeast rehydrating on the side while I do this. Boil the kettle, fill a jug, leave it to sterilise, and then pour most of the water out. Dissolve a spoonful of sugar in the remaining hot water, and then top up with cold until it's 20 - 25c. Sprinkle the yeast on top and cover with foil, give it 10 min or so, and then stir into the liquid, re-cover, and leave it until you're ready to add it.
Edit: the exception is candi sugar. Because it comes in big crystals it's a pain in the arse to dissolve. I dissolve that in the hot water in the stockpot, once the can is removed.