It sounds like you've made the first step toward a good Str8 shave experience. I have a question and a few suggestions.
1.) Is the seller supplying it in "shave ready" condition?
2.) If yes what ever you do don't strop it or touch it up in any way before your first shave.
3.) Start slowly and keep your angles low. No more than 1 to 2 widths of the spine away from your face.
4.) Don't apply any pressure while shaving. Let the razors weight do this for you.
5.) Start with short strokes and stretch your skin. It will help to flatten out your face contours and allow the razor to glide over them.
6.) You can use 2 hands (one at each end) to help steady the blade in difficult areas.
7.) Prep is important but you mentioned your currently using a brush so I'll assume you have no problem building a good lather.
8.) Relax and don't force the issue. If you don't get the full face the first few times don't sweat it. You need to learn new techniques.
9.) Let go of everything you know about blades. You said you know this is different so let yourself be a beginner and learn from the beginning.
10.) As a cook you know that patience is the secret ingredient to all good food. Follow the same logic with learning to use a Str8.
11.) If you can't return the first purchase then turn it into a learning piece. Dull it down so it won't cut you and use it for practicing new techniques in the hard to cover areas. It will at least have a similar feel and balance as your real razor.
Most of all lighten up and enjoy the journey.