Great article. I can confirm that these tips are helpful. I especially can recommend to start with doggy stile or maybe cowgirl and than switch too missionary or what ever you want.
I'd like to add some tips of my own:
You can use a shower with a focused stream option or unscrew the top to clean your ass. You will have to run from shower to toilette than. Don't do it to much (2-3 times and not too deep is good I think) - you'll get a feeling for this. You have actually 3 advantages with this: first you reduce the probability of having poop ruin your sex, second if you use nice warm water you can relax and widen your as a little already and lastly you are moistening the inside a little.
Than you should start with a finger than two and than slowly but in the penis or strap. I experienced that it is easier if you put it in and complete out again sometimes in the beginning. If you don't have lube you can also use lots of spit - it is cheaper and works just as fine for me.