I used three or four coats of RB ... I can't remember.
It did NOT fill the expansion saw cuts which are probably a little bigger than your 1/8" cracks. I would follow the recommendation of DoItMyselfToo if you went to do the best job of eliminating the cracks. Once I started working with RB I thought it would fill the saw cuts, but didn't. I didn't use a brush to fill with ... but I put lots of RB on the roller and tried to "work" the RB into the cracks ... but that didn't do the job.
How many SF are doing? I would suggest going with four coats ... I think that is what I did. I put five coats on the new plywood floor of the race trailer and I can still see the heads of the screws.
All in all, I like Rust Bullet. Happy with it.