Staining and sealing plywood shelves

I am in the midst of a project to colour and harden (seal) my kitchen, laundry and pantry shelves (in cupboards). They are made of plywood. There are currently a lot of spill marks on the wood and I'd like to prevent further marks and have a hard durable finish.

I did a patch test of stain and then applied satin estapol. Then the guy at Bunnings said I should put on neat linseed oil and then top with carbothane gloss (he said this was harder wearing than the satin). I asked him what the difference was between estapol and carbothane and he said they were completely different products and that estapol was not are hard wearing.

I've done the lindseed oil and it looks nice. I've applied 2 coats of carbothane and it appears to be soaking in, rather than sitting on top like the samples showed at Bunnings - i.e., still feels of wood and no gloss at all. Interestingly I noticed that the test patch is hard and high gloss.

Questions:
1) Why is the carbothane soaking in and not sitting on top to create a hardened barrier.

2) Why has the test patch with one coat of satin estapol hardened with the carbothane on top.

3) Should I be sanding between the coats?

4) How many coats should I apply? There are quite a lot of shelves and the carbothane says to wait 6 hours between coats.

5) Should I be using estapol or carbothane and what is the difference between the two.

Thanks to anyone who has some advice for me.

hi sussex .you have a difficult problem ,you took the promo sample as being honest .I dont know the diference btween the to paints but they are both air dried ansd as they drie they thin out and foum a very thin film .if u want to continue on u give the shelving a sand with wet and dry btween coats to knock off the peaks ,waiting till completely dry befor starting and use metho as wetting agent ,u will get the image result after maby 5 to 6 coats ,i know it sux but if u want instant results u can try 2pack which is expensive but it is an epoxy base which dosent shrink as it dries and a quick sand btween coats and the job is done after 2 coats and this is over 2 days as apposed to weeks and weeks of waiting for the paint to dry .and 2 pack is very durable .if u want good paint advice go to a pro paint shop or smaller paint supplier ,not a large chain store