I use a combo of all the methods you list, but given the time constraints, I’d be tempted to go with common sense.
Get on a whiteboard, or sheets of flip chart stuck together, and draft out your timeline along the top in weeks or months dependent on the timing of the project. Then list out key milestones against key dates on the main board. Have a look at those milestones and see how you could best group some of them to form workstreams E.g. ‘assess’ phase or ‘design’ phase. Then, along the left hand side, draft these workstreams or phases in the rough order in which they’ll start and shuffle your milestones around so they’re sitting in the right horizontal for their workstream or phase.
Now consider the ‘critical path’ for each of those milestones - what will have to happen in order to deliver them? Draft those activities in blocks that feed into your milestones.
Now consider the dependencies - what things will have to have been delivered to kick other things off? You might then have to adjust some of your timings - you’ll have to do this all the way through this process, as you work through activities and realise some will take longer or shorter than your initial thoughts. Any dependencies can be mapped with a thin dotted line from the activity or milestone to the thing that depends on it.
You should then end up with a decent visual plan, that you could draft up in PowerPoint - I find it easiest to have a table with workstreams down the left and weeks or months along the top, then map onto it chevrons for activities and triangles for milestones. This is useful for presentation purposes.
If you do this, you’ll have a really good grasp of all they key activities etc. You can then translate this into a fairly simple project plan using either MS Project or Excel - same principles, with overall work stream headings in the left column in bold and, sitting underneath each of them, discrete activities to deliver them. Each of these lines will have a number in both Project and Excel, and you can include a column called Dependencies in which you can just put the line numbers, separated by commas, for the activities that need to happen before that activity can be completed. You can then also add in dates due for each activity and percentage completed (Project can do this more automatically, but you’ll have to play around with it.
Hope that helps - shout if you need more info!