I wouldn't use a fuel filter, not nearly enough flow and the PS fluid is much thicker. The combo reservoir/filter that Howe and PSC sell are good, but you have to sort of redesign your system. I like the idea of using an off the shelf hydraulic fluid filter from a commercial application, that should be relatively inexpensive. I use an inline filter from Tommy Lee, Lee Mfg, which comes with either AN fittings or regular slip fittings. Mine has the slip fittings and goes between the cooler and the return to the reservoir.
Filters aren't necessary in PS systems, but they are a good precaution. There are many examples of folks chasing PS problems, replacing a component only to have it go out again, and they don't resolve it until they replace most or all of the system. The culprit seems to be small metal shavings from the bad part that contaminate the fluid and then end up taking out the new part, especially pumps. The filter is a safety valve that can contain any particles so the system isn't contaminated and the bad part can just be replaced. But, any filter used has to have enough flow to not create restriction and more heat.