To remove the shellack I would use paintremover; a tin of fluid acid that only reacts on the chemical lack but not with the organic material! Doesnt cost much and is bit acid to the skin (!). Apply richly to the handle >no worries< and wait (sometimes it take a while before working) and perhaps best is to whipe it off carefully with tissue in combi with an extra soft toothbrush for the holes etc. Or wash it quickly off with hot water (n toothbrush) and dry immediately after with tissue. Water will probably take more patine off than the 'dry tissue-whipe' method.
I am not a professional conservateur but this sounds pretty terrifying! I don't think any chemical paint remover should be used on any antique unless it has been proven to be harmless (long-term preservation rather than just cosmetic short-term appearance) on all materials involved.
Detlef, shellac is easily soluble in ethanol which will be much gentler to wood but still suck out some oils. What do you wish to remove, exactly?