You can do this- it's easy. You've done it once, so you have the basics.

I started driving tractors on my great grandpas ranch at 5 putting out hay with him, so I fancy myself somewhat of an expert-

1. Porsche keys are on the left, don't look stupid fumbling around for where to start it- that's just where Porsche puts them.
2. It's very much about balance. Porsche motors have plenty of go, but they are geared tall, so it's going to take more gas and clutch to make it roll. This is unlike Downshift's suggestion of a Dodge truck- that's got a tractor motor in it, so you can really ease, and I mean ease off the clutch and it'll go with no throttle. Remember BALANCE!
3. Car in neutral, push clutch in, start. Put in gear. EASE the clutch out while applying a LITTLE gas. EASE the clutch out, I can't stress this enough- this will give time to slip it a bit and get it moving. Once you're moving, you're golden.
4. Clutch out, you are now driving in first gear. Apply throttle just like you're driving your normal car. Tach will be very large, anticipate shifting at about 3500-4000 rpm. The last one I drove would make power all the way up to about 7000, but let's not do that yet.
5. Let's shift- apply gas until about 3500 rpm, probably going 30 ish (just a guess)- now you've got some momentum. Take your foot off the gas and push the clutch in. Shift to second, release clutch and apply gas again. Try to simultaneously get back on the gas just as you come back out with the clutch.
6. Wash, rinse, repeat.

When you want to slow down, push clutch in, foot off gas, press brake. Repeat step 3.

Just tell your associate it's been a long time since you've driven one. You'll get a bit of a nervousness yard pass.

To make you feel good - a few years ago my brother bought a GT500. He had NEVER driven a manual before. Not even a tractor. He had the car delivered to my house- I had a whole plan to teach him. He was so excited to get the car, he said, "screw you, I'm driving it". Stalled a couple times in the driveway maybe two more on the street, pulled out on the highway and he's been at it since. He daily drives it.