Tips for removing remaining stripper from a deck

I am currently stripping a large deck that was stained with a Sikkens cedar stain and am having trouble getting some areas of stain completely off. I am using F18 at about 6 oz. per gallon applied with a garden sprayer dwelling for about 20 minutes. Reapplying if it looks like it is drying too quick. Pressure washing with about 750 psi with a 40 degree tip to clean/rinse. For the most part it is coming off pretty decent but there are spots or strips where the stain is being stubborn(mostly it looks like it is in the grain). Is there any tricks to getting the remaining stain off or should I just keep retouching those areas with the F18 and pressure washing as I have been? Does my technique sound as though it is on par with what the rest of you guys use that do a lot of decks? This is my first “real” strip, neutralize and stain job. I am reapplying a Sikkens SRD Cedar Translucent stain to match what is on the railings. Any helpful tips or constructive criticism would be great!

What is the Sikkens stain you are trying to remove? If it is something nasty there is a good chance all of it won’t be coming off.