I hadn't heard of using washing up liquid or electrician's tape (which on reflection may have been better) but wrapped my bars (on one side) in masking tape, this worked fine at first but once at the bend in the bars started to tear the masking tape, luckily without marking the bars underneath. So I stripped the tape off, no screwdriver was used in the clamp as the stem is anodised black and I didn't want to mark it - even if it would have been hidden, and used copious amounts of WD40. This worked perfectly and the bars were unmarked. Plus, I got high.
I hadn't heard of using washing up liquid or electrician's tape (which on reflection may have been better) but wrapped my bars (on one side) in masking tape, this worked fine at first but once at the bend in the bars started to tear the masking tape, luckily without marking the bars underneath. So I stripped the tape off, no screwdriver was used in the clamp as the stem is anodised black and I didn't want to mark it - even if it would have been hidden, and used copious amounts of WD40. This worked perfectly and the bars were unmarked. Plus, I got high.