I have tried to foiling (Mylar) solid 3” lures and I found it very difficult, as they are hard to handle, glue up and foil, without fouling the glue etc. So I have been splitting the lures and doing a side at a time (to split, see tute: ‘Through Wire Construction’).
First, if you can get the Mylar gift bags (I find these the best) they already have glue on the Mylar, so this saves a lot of fiddling around. To get the Mylar off the paper backing, just give it a QUICK dip in some mineral turpentine and remove, dry excess off, with a tissue, and you should be able to gently peel it off (only do as much as you will immediately use). When you have your sheet of Mylar off, face down/glue up, weight it with some wire rods, as it will not curl up when the glue starts to dry again. The quicker you dip it, the more glue will release with the Mylar sheet and not the backing. Put aside and LET IT DRY.

Place the lure halves on a flat surface, with a bit of Glad Wrap under them, if the halves still have panel pins in them, all the better, because you can force these into the backing to steady them (I use a cork block). The lure halves must be sealed or primed and sanded smooth, what you have underneath the Mylar will show through the finished Mylar, this includes dust specks, so make sure they are sealed first.
As all contact glue (I have used) says, you have to “GLUE BOTH SURFACES, AND LET DRY”, so you need to apply contact to the lure body also.
Get some contact glue (green snotty stuff - not spray) and place enough to coat both lure halves on a sheet of plastic or glass, then add mineral turpentine, to thin it down (about 4:1) to a watery liquid (use this so it does not flash too quickly). Now, either paint glue onto lure or use your finder and apply EVENLY and THIN to lure halves (working quickly), making sure you work right to the edges. If the glue is thinned enough, it will not drag when you are applying it and will feel very slippery – if it starts to drag, dilute it a bit more.
When all is good and evenly coated, cover the blanks and Mylar with something to stop dust settling on it and let it dry - DRY for 12-24 hours, as, if there is still solvent in the glue it will gas off and blister the sheet when the lure is top coated.

Now the hard part - Sticking the Mylar to the lure. –
Clean your hands and lay a piece of Mylar on the side of the lure at the highest point of the side (which would usually be the flattest part of it). Watch out, because it will grab it, so closely align it before you place it. Stretch and smooth along the flat portion, working from the centre out to the edge of the flat, work out any wrinkles (if wrinkled, try and lift it and stretch it out). Now pull the Mylar toward the crest on the back centre, and lay it against the glue, it should grab and stay there – work along the lure, from top centre to back, and then, centre to front, don’t be afraid to pull and stretch it (it’s a bit like upholstering a chair). Next do the same on the bottom, going centre bottom to back and front, look for wrinkles and try and lift it an stretch them out – when you’re happy smooth the whole lot out with a soft cloth and heaps of pressure. Where two curves meet, you may get an overlap of Mylar – make a cut along the fold and overlap so there is coverage and trim off waste – be careful when cut as it will easily tear. Do the same to the other side, check the edges to make sure they are glued, then lightly sand the flat (joint side), and edge, to trim off excess Mylar. Mix up some D2T and glue together, making sure there is heaps of glue so it fills the joint. Sparingly, wipe off excess glue, with some alcohol, put it aside and let it set on a wheel if you have one, so the glue does not run out. The rest is up to you. pete