I don't agree with the guy at the paint shop. For every product that requires a separate coat you are increasing the risk of making mistakes. I have painted several cars myself with true show quality results, but not straight out of the gun. It has been several years since I painted a complete car and I too was surprised at how much the materials have increased in price. My recommendations is as follows:
1. Preparation Your final result will only be as good and as durable as what is under the top coat. Unless the paint on the car is very sound and not several coats, it should be removed. Laying new product of different types of paint and over old paint can cause problems down the road. Also you should degrease before you ever start sanding and do so often during the process.
2. Primers. Whether you strip completely or not, your first primer should be a 2-part epoxy. The next should be a high build surfacing primer.
3. Use high quality body filler where necessary and always allow plenty of time for all body work to age so that you do not get shrinkage. I would never try do everything within a week and expect it to last for several years.
4. Paint. There are a lot of options. I think the easiest is an acrylic enamel with a urethane hardener(PPG Delstar-Delthane). Put on a light tack coat and allow to flash dry. Follow with 3 wet coats allowing to flash between coats. No clear coat just color
5. Polish. Color sand wet starting with 1200 grit and move up to 2000. Buff using a foam pad and fine compound. Finish with an ultra fine compound and swirl remover.
This will produce a show finish. If you do not have a paint booth, any small amount of dust and orange peel you get in the paint will be removed in the sanding process. It is impossible to get a good finish without polishing unless you have the right equipment and talent to lay the paint smooth. Most of us amateurs are not going to be that good.
This system has worked for me, but it is by far not the only method and it does require skill as well to polish and buff without damaging the paint. The paint on my Sprite is nearly 30 years old and although chipped, it still looks like a paint job that is only a few years old. It was one of the first I did with this method.
One place to look for paint at a more reasonable price is:
https://www.tcpglobal.com/autocolorlibrary/default.aspx
They will custom mix your color in PPG or there own brand Restoration Shop that is less expensive. They have the PPG paint chips on their site.
I found Carmine in the Triumph section:
https://www.tcpglobal.com/aclchip.aspx?image=1976-Triumph-pg02.jpg
I hope this helps a little. I am not an expert by any means.