This sounds like my best plan . I have been filling takes with black garden hose and I know that is a nono . I just bought a white hose but have not used it yet . The water has just a little smell but not bad . A portable filter to filter the water before the tanks sounds perfect . I think I already have a canister somewhere . I winterized my lines last year and my hot water heater, not going to do that this year . Thanks
Look at the Pentek DGD-2501 filter, in a 10" Big Blue housing. (filtersfast.com has 'em). It's a dual-gradient sediment filter, outside 25 microns, inside 1 micron. Doesn't seem to affect flow rate when I use it hooked up to the shore water connection, either.
Then consider a carbon block filter on water to be used for drinking, or coffee or whatever. When we fill our tanks, we use a smaller (diameter) secondary housing with a Pentek FloPlus-10 carbon block filter (.5 micron)... but that does affect flow rate, so we don't use that when connected to shore water. (It'd maybe be overkill with many shorewater sources, anyway. And we don't actually often hook up to shorewater, anyway; we mostly use water from our own tanks for everything.)
A possibly better solution might be a carbon block filter on a purpose-specific water faucet... something like Moen's SIP system which we have in our house. I've been intending to install something like that -- to supercede that secondary filter above -- at our galley sink, but haven't gotten a round tuit yet.
All that said... it's good to drain/clean/sanitize your freshwater tanks first, though. Just running clean fresh water through those won't really clean the tanks of existing sediment, crud, whatever.
-Chris