You'll have maybe an hour overall to enjoy the lounge. You will disembark the plane, go through DXB transit security, then go back up the elevator to Level 3. Then you will walk over to the lounge elevators, up to Level 4. Show your ticket and you're in. Note your gate assignment; while the lounge stretches the length of the concourse, the entrance is in the middle and the lounge is almost a carbon copy on each side, same amenities on both sides other than possibly a high end alcohol shop if you go left after the lounge desk check in. So, since you don't have that much time, simply proceed to whichever side has your gate, unless seeing giant bottles of Moet & Chandon is your thing
. You could sit down and have a restaurant meal with servers, or get a shower in, or pick from the multiple prepared food areas if you don't want to wait, including pretty much anything you can think of (I'm partial to the sushi).
You will board directly from the lounge, which involves going to the gate sign for your flight and proceeding to a gate desk, where an agent will check your documents as normal. Then, you go around to a set of elevators, and you'll go down to the lower level. With EK, you would get off at the upper deck level as F is on the upper level, but with QF you'll get off at the lower level since F is on the lower level, and then walk over to the F jetbridge. You'll have to share this part of the boarding area before the jetbridge with the economy people for a precious few seconds, I know this is a big ask of some people here
. However, you won't have to share the elevator with the business class customers (you possibly could if boarding an EK flight out of the Concourse A F lounge) so that is a plus
.
In short: Exit plane, transit security, up to lounge, enjoy eating/showering/relaxing/photos, board directly from lounge via elevator, back on plane and on your way to your next destination.
Experience: I've done LHR-DXB, DXB-SYD, and MEL-DXB-LHR (under the old schedule), and also passed through the Concourse A lounge a third time with a much longer connection on EK F.