I've got a little experience with repainting chromed grille pieces and I can tell you that the Plastidip will not hold up like it does on wheels. The sand blasting effect that the front of our cars get quickly pits and erodes almost anything applied and soon the chrome starts poking through. I have had great success with using POR-15 as a base coat over the chrome. The stuff is basically a moisture cured urethane that sticks to the chrome like epoxy. It also sticks to your skin like super glue because that is pretty much what the stuff is, so if you spray it make sure you wear a canister respirator. It lays pretty flat by simply brushing or rolling it on.
When the base coat of POR-15 is still curing (maybe 20 minutes after application) spray a couple of top coats of the paint colour of your choice. I used Krylon semi-gloss black. The top coat of paint will start to fail after about a year, however since the base coat is a bulletproof flat black, it won't be as noticeable and definitely doesn't chip down to the chrome. It is fairly easy to re-coat with another layer of colour topcoat each year. POR-15 fades when exposed to sunlight so it must be top coated.
I used this method to successfully change the ugly 3 bar chrome grill of my old Ford Fusion to body match colour. I shot the top coat in PPG's Omni line of base coat/ clear coat urethane paint and it still got sandblasted off each year but the black POR-15 base coat always saved the day.
Hope this helps. I currently have an aftermarket blacked out GTI grille on my '09 TDI and painted the chrome grille emblem as described above. It's due for a recoat but still looks good at 6 feet away.