Buttercream and Ganache Timings

Hi all,

First post and not sure how to search the forum on my phone, so forgive me if this has been asked before.

I’m pretty new to cake decorating, this is only cake number 3 or 4, but I’m a perfectionist! In previous cakes, I’ve had a slight buldge at the layers, nothing major, but enough to annoy me.

I’m trying ganache under my fondant for the first time for this cake, but I want to fill the layers with jam and buttercream. I’ve read about the dam method, so will try that too. But I was looking for opinons on the timings of it all. Here’s what I’ve got:

Cake is needed Thursday (evening, but working all day)

Sugar paste decorations already made (minus a flag which was going to be slightly draped over the side of the cake but cracked massively when I tried to move it today, so I’m figuring I’ll need to remake it once I’m ready to put it straight onto the cake?)

Was planning on baking cake, wrapping in cling film and refrigerating overnight.

Should I buttercream before refrigerating the cake (once cooled obviously) or should I wait til the next day? Should I refrigerate another day after filling, before ganaching (upside down method), or is it ok to ganache an hour or two later?

After ganaching, can I cover with fondant as soon as it’s dry, or should I leave it at room temperature overnight (I live in Scotland, so there shouldn’t be any humidity/heat issues)? Again, I work full time, so each ‘overnight’ step would need to have 24 hours or so between them.

Thanks in advance!