Getting used to a Saddle...

Not meaning to insult your intelligence or knowledge, so please don't take this that way.

Are you wearing bike shorts or tri-suit/shorts with a pad (and going commando)??  That's the first thing.  How's your fit on your tri-bike?  That can have a profound impact upon how well your nether regions tolerate riding.  While alternating between the roadie and the TT bike will allow you to get miles in, it likely won't help with the acclimation process.  It takes time and miles.  Sadly, you may be a bit uncomfortable for some of that time.

Personally, I went saddle shopping very early on.  I'm not going to say which saddle I ultimately decided upon - only because saddles are so incredibly individual.  I will say, if you want to start looking at alternate saddles, you might consider Cobb.  They have a VERY generous return policy that allows you to try the saddle for multiple rides to make sure it works (I should qualify that, they HAD, the company was recently sold so I'm not up to date on what the current policy is, although I'd be surprised if it's dramatically changed).

https://speedandcomfort.com/collections/triathlon