With the Main Range Np, Mt Barney Np & Lamington NP (Binna Burra section) & there remote campsites closed, your choices in SE Qld are a little limited at the moment.
You could base yourself at Green Mountains, Lamington & do the longer circuits. I think the drive-in campsite is still being upgraded though. Cooler & green.
The Border Ranges NP, it's walks & drive-in campsites are is still open. Booyong walk 9km one way, between Sheepstation & Treetops camps. Brindle ck walk. Cool & green.
Glen Rock State forest is still open, dry open country though. Good ridge walking. Remote camping. Take water.
Mt Warning summit will get your thighs burning. Bleary eyed early start required. Cool & green.
Springbrook NP has the longer Warrie waterfalls circuit 17km...nice walk & swim options. Settlment camp is open, Woonoongoora walkers camp should be too. You could use the Gold Coast Great Walk from settlement camp until the walkers camp, then return. Cooling swim option at the river crossing.
Wyaralong, Mt Joyce summit & it's off track ridge circuit walk is open. Ngumbi camp open. Dry area walking. Take water. Nice views from Mt Joyce.
Plunkett conservation park, ridgeline walk to Wickham NP...dry area walking. Lots of circuits & side track options for training & variety.
Flinders Peak & Mt Blaine summit + Flinders Goolman trail. Dry walking,
Not the 2/3 day long walks your looking for, but that's all I can think of for practice, off the top of my head....while our bread & butter Np's are still closed.
Last edited by ofuros
on Sun 12 Jan, 2020 3:27 pm, edited 3 times in total.