Stock refinishing question

[Mr. 16 gauge]

I have a Marlin model 60 that I bought used a few years ago....not a great gun, but I figured the price was right. Took it to the range and it jammed quite frequently; I took it apart, gave it a good cleaning/scrubbing, and it is pretty reliable now, and not too bad in the accuracy department.

I decided that I for a summer time project I would refinish the stock and touch up the metal...make it look a little 'nicer' and 'newer' (although it doesn't look to bad as it was).

Anyway, I decided that I would like to try to checker the stock....figured if I screwed it up, it was just an inexpensive .22. I have sanded down the old finish and sanded off the little squirrels & oak leaves that Marlin burned into the stock (what a pain!).
I have refinished some stocks in the past, and recut some bad checkering, so I do have a handle on the basics, but I've never done a 'new' checkering job on a blank stock.

What my question boils down to is this: Should I put the stock filler/conditioner on before I do the checkering, or after?

...or, could I just skip the filler and use subsequently finer grits of sandpaper and sand the stock down, then cut the checkering and finish with the tru-oil (I'm using Birchwood-casey products; it's what I've used in the past and the results turned out very well for me).
Thanks in advance.............