bare footed for a good grip using the lowers and mast surface for traction ...... and the helper 'follows' with a halyard as a safety belay, tightening and loosening as needed.
Its the damn splices and worn out eye splices on old rope that are the most dangerous - either use a 'safety jumper' (lightweight small diameter line/sling using prussiks) **across** the splice or forget the splice and tie in behind the splice using bombproof knots. I gives me the 'absolute willies' to see folks climbing a mast on worn-out old crap UV burned halyards with 'doubtful' splices terminated into 'shackles'.

As a former paramedic, one of the absolute worst cases I had was a mast climber whose 'harness' broke, fell from the spreaders down to the deck and got impaled on a stancheon. Luckily a medevac helo was just passing-by and the stancheon was easily removeable and where it penetrated wasnt fatal.

If your going up the mast often, forget 'plain vanilla' climbing techniques and learn to do 'rescue climbing' techniques/methods - 'safety jumpers' across all 'knots' and connectors; do use a safety line, and learn how to tie 'mountain RESCUE knots' - doubled terminal figure 8's, etc. and not BS 'bowlines', etc. .... so you have 'reserve' strength in the line and climbing equipment to free fall at least 20 ft and not have the 'knots' capsize and break.