I've had my shoes polished by shoe-shine boys in a few 'third-world' parts of the globe, but have avoided it so far on this journey.
You see, the boots I'm wearing are supposed to be of high-quality leather, water resistant, in addition to the water-proof membrane included. So far that has proved to be the case (unlike some of the other 'high quality', 'rugged expedition' apparel I bought for the voyage). And as I understand it, such leather needs to be cleaned properly otherwise the dirt impregnates the leather reducing its water-resistance, and ditto the stitching, reducing the strength and water-resistance of that. Now my boots have been permanently covered with African and Middle Eastern dirt, dust, sand and even mud on this journey, except for the three or four occasions I've washed them before applying some leather dubbin. Consequently, whenever I cross some pavement corner wearing these grubby boots I hear a chorus of shoe-shine boys imploring me to stop for a quick polish.
So until now I've resisted, not wanting someone to slap polish on top of the dirt and sand and rub the whole lot into the leather.

But here in Gonder, a town with a goodly supply of shoe-shiners on the pavement corners, I noticed that a couple of them, outside a very nice pastry café, have tubs of water next to their cleaning paraphernalia.
I asked if that's for washing the shoes first.
"Of course, washed clean before polish. Sit down, I get fresh water straightaway!"
So he did, and I did, and I proceeded to partake of the best shoe-shine ever.
Then I noticed a certain embarrassment. As he enthusiastically washed all the dirt off with water and brush, my laces came into full view. They have both broken twice so far, and each time I just knotted the broken ends together in-situ and re-tied them. So with all the dirt washed off, all the knotted and frayed ends became prominently visible.
The guide books for Africa all say the same about dress - to be taken seriously you have to wear clean clothes in reasonable condition, whatever style they are. And it's true. Everyone you see on the streets wears sparkling clean brightly-coloured clothes and shoes. Even the white top-to-toe robes of the Sudanese men are always whiter-than-white, despite the air, pavements and roads being heavily laden with dust and sand. The consumption of washing powder across Africa must be the highest in the world.
And this shoe-shine executive was the same; smart clean shirt and trousers and of course shiny shoes.
Now my broken frayed and knotted laces looked a bit of a mess. So I hatched a cunning plan.
By the time my boots had been washed, waxed and polished they looked as-new again, truly for the first time since I bought them. But the frayed knots in the laces completely ruined all the fine work and flamboyant polishing of the smart shoe-shine boy. So I paid (fifty pence for shoes, one pound for boots, probably more than the locals pay) and explained carefully I would be back shortly with another task. He nodded and smiled but I wasn't very sure he understood me.

My plan was to nip back to the hotel, retrieve a spare pair of laces from my luggage (as they are well over six-foot long and not easily obtainable I have a few spares but haven't bothered to use any), and return to the shoe-shiner. Then thread them in so he could see the proper results of his labour with decent laces fitted, and leave him the old ones and a small tip. I had noticed that his equipment was tied into bundles, and his boxes tied up, with old shoe laces. Like all of Africa, nothing is ever thrown away, everything is re-used for some new purpose (except, of course, plastic bags).

On my return he ordered me to sit down again when I showed him the new laces. He brushed my hands away when I attempted to remove the old ones, insisting on doing the job himself. With old laces gone, he opened out the uppers completely, revealing a whole load of caked and compressed dirt and sand around the tongue. So he started again with water and brush, cleaned it all out, applied leather cream and polish, brushed and buffed until each complete and unlaced boot gleamed in the sun.
And with a final flourish, threaded up the new laces to complete the job properly and refused any further payment.

They say, back home, if you want a proper job done you have to do it yourself. I'll try to remember that doesn't apply to shoe cleaning in Africa.
(Nor, from what I saw in Khartoum, car cleaning).