when your upshifting alittle common sense goes a long way. You will just need to shift slightly slower than when you shift normally using the clutch. Down shifts you will need to rev match.

By shifting without using the clutch we can determine if the problem is with the clutch not disengageing fully or if the tranny needs servicing.

If its the tranny you could try using some redline or lighter tranny fluid than whats in there now. If it really becomes a problem trannys are pretty cheap. (Cheaper than a rebuild)