Hi Fuzzy, my Builds # 1 & #2 were done with DT Stain & Intensifier followed by multiple coats of TO. Applied first couple of coats with a 1" paint brush and bodies soaked up plenty and this helped to pore/grain fill. Wet sanded with 1500 & 2000 and you will not find this stuff at the big green shed. I ended up buying some at Autobarn as this fine grade of paper is often used in finishing cars. The trick is to just smooth things off a bit and not take too much of the extra fine coats of hand rubbed TO off in the process. Eventually bought some micro mesh pads that range from 4000, 6000, 8000, up to 12,000 and are great for final prepping before applying Maguires polish.
To apply TO as the wetting agent and using 600 grit paper may just be to coarse and end up stripping layers of stain off or thinning it down as using dry 0000 steel wool can do the same thing if not careful.
For Builds #3 & #4 I brushed initial TO coat on one as I was nervous that ragging would cause issues with colour potentially bleeding and ragged the other. Main difference I have noted is that on the one ragged straight up seems to need pore & grain filling, if I can be bothered, as being ash it has helped to accentuate the grain even more. Will wet sand starting with 4000 micro mesh pad on the weekend on both to see if that helps with the small amount of levelling required.
Short answer, best to wet sand after 4-6 coats of TO as it goes on very thin and too coarse a grit will strip it back in no time.