Why don't you just drum more, except drum harder when you practise... Surely that's the best way?
Failing that, get a towel and dip it in a bucket of water, ring the towel out, repeat. Get a bucket of sand, and push your hands through, rolling them about like almost digging through the sand. Do that constantly. Could also try wrapping a smaller towel, like a dish cloth round the handles of two buckets filled with sand and just carry them about. Farmers walk style.
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