Fuel Filter and bleeding question

[Mike and Joanne Stimmler]

I have read most of the posts on replacing fuel filters and bleeding the system but are there any special considerations if I'm replacing both the primary and secondary filters at the same time?
I've also managed to find the P S diesel additive that Ron recommended and am going to give it a try. I forget whether the secondary filter is horizontal or vertical. If vertical can I fill it with the additive as well. I'm a little skeptical about putting anything other than diesel fuel directly into the system, but if Ron says it'll work then I'll give it a shot.
Thanks,
Mike

[Ron Hill]

Mike : Both filters are vertical, but as I mentioned change one, start the engine and then change the other and start the engine.
Let the engine run for about 3-4 minutes each time.  That way if the engine were to stop you know which filter needs to be re-bled!
If you're concerned about pure PS additive only fill the Racor with 1/2 additive and the rest with diesel!!  But fill each filter with something besides AIR.   

[Mike and Joanne Stimmler]

Replaced both filters this past weekend and everything went just fine. No problems using the PS additive but I suspect that it got dilluted when I opened the bleed screw and some of it going back through the return line. Also did the transmission fluid and heat exchanger zinc. No problems there either. Still working on the motor lift though. I have to fabricate a mounting plate to fit the top of the transom. Thanks for everyone's help.     
Mike

[Ron Hill]

Mike : Glad everything worked out well. 
Know you know why I use 100% PS additive to fill the filter - so you still have some concentrated additive after you use the bleed valve!!