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I don't know if you've got the same 4" dob as mine or another brand, so it might not have the same f number. Mine is an f4 but my 76mm tabletop is f9 and Jupiter is fine without a filter. A moon filter would work (they're usually a green colour though? so that might hinder contrast in the bands on jupiter). A Neutral Density filter will tone down the brightness but not effect the colour.
Get up early in the morning and take a look at Jupiter, easy to spot. Depending on your scope, eyepieces and eyes it might look natural to you, or maybe too bright. Decide for yourself if you feel you need a filter. Also a barlow should "stop down" an eyepiece, making the image dimmer. In photography there is always a trade off in amount of light captured when you change focal length (magnification), so your best magnification eyepiece might be fine enough.
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