Everybody does veneer grafts. Always make you flap on the understock a little longer than the length of the cut on the scion and secure with your bud strip. The width of the cuts should be the same also, if you don't get an exact match on width, match up at least one side, perfectly.

Use parafilm tape on:
Spruce
Hard Pines

Here's a photo:
{{gwi:311170}}

(The scion has cuts on both sides - notice the angle cut on photo called "scion #1" - the scion is rotated clockwise 90 degrees to be inserted when both cuts have been completed)

Never cut into the scions or the understocks more than 1/3 and on Spruce even less.

The grafts must be tented inside your prop house to maintain humidity.

Use bottom heat.

Check each morning if heavy water droplets are on the foliage, if so lift the poly and let them dry off and then close the tent structure for the day.

The scion must be dormant, the understock must be alive. Your window lasts between Dec - the end of Feb generally speaking. Keep your prop house at 50-55 F if you can.

Dax

Thanks very much DAX. This was just what I was hoping to see. Maybe we will see others also.

As with Apples your imagination is your own limit. This is a grafted tree with each branch having a different dwarf cultivar:

{{gwi:866640}}

A Pine graft after 6 months (the above understock is removed and the scion is the only thing left)
{{gwi:311171}}

This is a Fir graft where extra scions were attached to a Fir understock (extra scions and not enough understocks) so that the scions could be recycled. You may be able to notice that part of the original understock was kept and used and attached the following winter to this new understock:
{{gwi:866641}}

A couple more tips:
Leave the understock above growth on for one full year on Spruce trimmed to one branch. The others (such as the 6 months pinus) remove them before fall of that same year. Some brooms will die if the understock is removed and some won't. Most won't. It's up to the grafter to find out what needs to be done.

Only water when they are getting dry or you'll rot em and cause disease problems.

Keep a shade cloth handy for days when the prop house might/will become too hot anytime.

Don't let them get too hot or too cold. It's your job to babysit these until they're ready to be taken out of the house. You should pot em up when weather permits or anytime up till around June if you don't get to it right away.

When all danger of frost has passed, bring the grafts to a shade structure or similar such as under a large tree so they do not receive full sun. They'll turn into toast if you don't. After one or two years the grafts will be ready for full sun.
As soon as you graft, it's a good idea to hit em with a fungicide or combo fungicide/algaecide. Spray them right away then. After that, when the scions push, hit them again. Moniter the plants for disease and spray when necessary otherwise removing plants that might infect others. These first two times are kinda crucial. I'd recommend you do so. I happen to use Consan 20 because it's available at my local garden center, but another good one is Zerotol 1:10 (1 part Zerotol to 10 parts water). Read the directions man.

That's about it I believe.

Take care & best of luck,

Dax