I disagree with Alex Nislick regarding the Mast Mate Ladder. Years ago I had an opportunity to use a product of this sort and did not like it. It has all the problems of mast steps - narrow footing base so you swing around while climbing - with the added disadvantages of flapping around and taking time and hard work to set up.
As a solo sailor and one who takes on rigging jobs on diverse boats I found that a proper chair/climbing harness and a couple of ascenders do the trick. Some boats have internal or wire halyards so you may want to bring your own length of dacron rope for setting up the easiest rig:
Nothing more than a loop from your harness up to the masthead pulley down to a pulley held conveniently low (mast base ring, low bale, even the gooseneck or whatever) and back to your harness. Put your ascenders on the fall - both with footloops that suit your size and one als with a short line to the harness - and start climbing.
Since you're pulling on the fall, each step takes but half the effot of climbing a fixed rope.
The slack that otherwise would be piling up on deck is something you're taking aloft with you. This also keeps some weight on the fall as it runs down past the ascenders, making it easy to push them up.
You can adjust the tension on this rig at any point so you can swing out to the spreaders or even jump back or forward to get at something fouled in a stay.
Because it's not a fixed line, you can transfer your weight from the ascenders to a descending ring and come down quickly.
Like any work aloft, it takes a bit of practice and familiarity with the gear. The advantage of this system is that you really won't go far without mastering it, so you won't put yourself at ignorent risk.
All the parts are readily available from both rigging suppliers and mountaineering shops.