When I first started tiling, I tried to do it the "proper" way, i.e. spreading the muck on the wall then sticking the tiles to it.
Could never manage it well, so moved to "buttering " each tile individually. Got on much better, and much less mess. Only problem was if i put too much gunk on and had to take the tile back off, scrape it off the wall and tile, and restart.
I always use 2mm cross things but I don't put them on the wall like you should, I put them sticking out of the wall and use eye-n-bubble, to make sure they are aligned. The last lot I did was rectangular ones, brick style, so the crosses would have been a pain.
The thing i learned recently, the hard way was how to do external mitres. and i wish i had started in the utility, cos having got it a bit wrong in the kitchen, i'll get it right in the utility!
The other difficult thing is using coloured grout. Don't know if you have used it, it does look fab, but I wouldn't dream of using, or trying to use a whole bag at a time. I may be doing it wrong, but I could never use it quick enough, so I mix it up well, in the bag, they weigh out an amount, mix it with a measured amount of water and then stir it up and get on with it. After a while you get a feel for the consistency which is good because even measuring it out as described there can be inconsistencies in it and you may need to add either more powder or more water.
When I first started grouting, I did each line separately, it was taking for ever. So Wifey suggested bunging a whole load on then scraping off the excess, and carrying on like that. so I am a lot quicker now. I also use a fancy grouting tool that has different profiles in the corners, which makes it all much neater, quicker and more economical.
https://www.victorianplumbing.co.uk...VELrtCh2L5wxaEAQYCCABEgJsNPD_BwE&gclsrc=aw.ds
is LIKE it but mine has a better surface, can't remember what it is called, silicon maybe?
Last tip, the coloured grout people also make silicon sealer to match which is absolutely fab!
https://www.screwfix.com/p/mapei-ma...VJu_tCh0loAsPEAQYASABEgKkpfD_BwE&gclsrc=aw.ds
Anyway, best of luck with it!
Wish I was as good at separating rusty bits of Discos.