If I remember correctly, the OEM spec is 10w fork oil. Maxima racing fork oil is what I generally use. You're right in that your fork oil is likely shot and really not doing the job anymore. If you want additional improvement in feel, you should change the fork springs while you have everything apart. Stockers tend to be too light for a lot of people. You can get springs for right around $100 (+/-). Using your weight while wearing your gear, there are calculators available (the racetech site has one) to determine the spring rate you need.
If you decide to change the springs, there are multiple threads here that cover it, but if you were to get hung up on anything there are folks here that can guide you.
I expect others will chime in here as well.
Edit:. I'm slow. Was typing when Badmoon responded.
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'96 DR650, '01 SV650, '10 Aprilia Tuono 1000R