Treating my raised beds...

I bought some untreated wood and am planning on treating it.
I'm doing the SFG thing with 2"x8"x4ft pieces. 4 make a bed.
I am doing 4 beds so with 16 pieces I've come to the figure
of 110 square feet of surface area that must be painted.

I want to do 50% Pure Gum / 50% Raw linseed coat.
When that drys I want to do a Boiled linseed coat.

I guess my question is, how much do I need of these ingredients?
Do I need to do 2 coats of the first mix?
Does untreated wood take to these oils easily or will much need to be used.
Is it even worth it to treat untreated wood with linseed oil?

Also, I have heard of pulverized charcoal mixed with boiled linseed oil. Would this be a better option.

As always, price is important, among other things.

Thanks in advance for any help. I greatly appreciate it.

Andrew

PS: I'd probably need to treat the 4ft x 4ft plywood underneath the beds as well..

just a comment..if possible I would strongly suggest you DON"T put a floor in them (unless they are on concrete or your patio  or there is some other compelling reason).  I have several with floors and two without and the ones without, the plants do a lot  better..watering is much less of an issue for one thing.  I have a squash and a cuke planted in raised beds with floors and a couple of squash in one of the ones with no floor and the squash with no floor are twice the size. We recently had a couple of severe storms; one with hail that just decimated the plants in the floored boxes (and in most of the gardens in a 3 mile strip as well) but the sunflowers and squash in the raised boxes with no floors just bounced through them.

At the end of the month I am turning all the floored boxes over and taking out the floors, then just using the frames to contain everything for next year. I expect a bumper crop next year as the plants were producing in the floored beds, it's just they needed LOTS  of watering (almost a gallon per plant!) every darn day when it was  hot or they wilted and the tomatoes catfaced. Also the lettuce LOOKED wonderful but oh boy was it bitter.  If I didn't miss the water the tomatoes were wonderful.

The other alternative would be  to do the wicking box watering system in them but then the boxes end up only having about 8 inches deep soil & that seems a bit sparse if you are asking for any amount of production. So no floors seems the way to go..